From e87a929300f82e8b7608039f143b1533b51af4e0 Mon Sep 17 00:00:00 2001 From: Mavridis Philippe Date: Sat, 5 Feb 2022 17:44:26 +0000 Subject: Add tdemarkdown part - embeddable lightweight markdown viewing component. MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit TDEMarkdown is based on the md4c library and using TDEHTML for rendering its output. For enhanced safety, on HTML widget is turned off everything we don't need for viewing. It integrates nicely into Konqueror and supports both Commonmark and GitHub markdown syntaxes. Signed-off-by: Mavridis Philippe Prepare to merge tdemarkdown into tdelibs. Signed-off-by: Slávek Banko (cherry picked from commit 95279fbf6dfeb43d80590740a9259d7caa614177) --- CMakeL10n.txt | 1 + CMakeLists.txt | 1 + mimetypes/text/CMakeLists.txt | 1 + mimetypes/text/markdown.desktop | 11 + tdemarkdown/CMakeL10n.txt | 8 + tdemarkdown/CMakeLists.txt | 67 + tdemarkdown/LICENSE | 117 + tdemarkdown/README.md | 14 + tdemarkdown/markdown_part.cpp | 133 + tdemarkdown/markdown_part.desktop | 10 + tdemarkdown/markdown_part.h | 47 + tdemarkdown/markdown_part.rc | 4 + tdemarkdown/md4c/CHANGELOG.md | 442 + tdemarkdown/md4c/CMakeLists.txt | 59 + tdemarkdown/md4c/LICENSE.md | 22 + tdemarkdown/md4c/README.md | 297 + tdemarkdown/md4c/md2html/CMakeLists.txt | 22 + tdemarkdown/md4c/md2html/cmdline.c | 205 + tdemarkdown/md4c/md2html/cmdline.h | 153 + tdemarkdown/md4c/md2html/md2html.1 | 113 + tdemarkdown/md4c/md2html/md2html.c | 383 + tdemarkdown/md4c/scripts/build_folding_map.py | 120 + tdemarkdown/md4c/scripts/build_punct_map.py | 66 + tdemarkdown/md4c/scripts/build_whitespace_map.py | 66 + tdemarkdown/md4c/scripts/coverity.sh | 70 + tdemarkdown/md4c/scripts/run-tests.sh | 75 + tdemarkdown/md4c/scripts/unicode/CaseFolding.txt | 1584 ++++ .../scripts/unicode/DerivedGeneralCategory.txt | 4100 ++++++++ tdemarkdown/md4c/src/CMakeLists.txt | 56 + tdemarkdown/md4c/src/entity.c | 2190 +++++ tdemarkdown/md4c/src/entity.h | 42 + tdemarkdown/md4c/src/md4c-html.c | 573 ++ tdemarkdown/md4c/src/md4c-html.h | 68 + tdemarkdown/md4c/src/md4c-html.pc.in | 13 + tdemarkdown/md4c/src/md4c.c | 6410 +++++++++++++ tdemarkdown/md4c/src/md4c.h | 405 + tdemarkdown/md4c/src/md4c.pc.in | 13 + tdemarkdown/md4c/test/LICENSE | 64 + tdemarkdown/md4c/test/cmark.py | 40 + tdemarkdown/md4c/test/coverage.txt | 522 ++ tdemarkdown/md4c/test/fuzz-input/commonmark.md | 40 + tdemarkdown/md4c/test/fuzz-input/gfm.md | 10 + tdemarkdown/md4c/test/fuzz-input/latex-math.md | 1 + tdemarkdown/md4c/test/fuzz-input/wiki.md | 1 + tdemarkdown/md4c/test/fuzzers/fuzz-mdhtml.c | 35 + tdemarkdown/md4c/test/latex-math.txt | 39 + tdemarkdown/md4c/test/normalize.py | 194 + tdemarkdown/md4c/test/pathological_tests.py | 128 + .../md4c/test/permissive-email-autolinks.txt | 50 + tdemarkdown/md4c/test/permissive-url-autolinks.txt | 99 + tdemarkdown/md4c/test/permissive-www-autolinks.txt | 107 + tdemarkdown/md4c/test/spec.txt | 9756 ++++++++++++++++++++ tdemarkdown/md4c/test/spec_tests.py | 144 + tdemarkdown/md4c/test/strikethrough.txt | 75 + tdemarkdown/md4c/test/tables.txt | 357 + tdemarkdown/md4c/test/tasklists.txt | 117 + tdemarkdown/md4c/test/underline.txt | 39 + tdemarkdown/md4c/test/wiki-links.txt | 232 + translations/desktop_files/mimetypes/mimetypes.pot | 7 +- .../tdemarkdown-desktops/tdemarkdown-desktops.pot | 27 + 60 files changed, 30044 insertions(+), 1 deletion(-) create mode 100644 mimetypes/text/markdown.desktop create mode 100644 tdemarkdown/CMakeL10n.txt create mode 100644 tdemarkdown/CMakeLists.txt create mode 100644 tdemarkdown/LICENSE create mode 100644 tdemarkdown/README.md create mode 100644 tdemarkdown/markdown_part.cpp create mode 100644 tdemarkdown/markdown_part.desktop create mode 100644 tdemarkdown/markdown_part.h create mode 100644 tdemarkdown/markdown_part.rc create mode 100644 tdemarkdown/md4c/CHANGELOG.md create mode 100644 tdemarkdown/md4c/CMakeLists.txt create mode 100644 tdemarkdown/md4c/LICENSE.md create mode 100644 tdemarkdown/md4c/README.md create mode 100644 tdemarkdown/md4c/md2html/CMakeLists.txt create mode 100644 tdemarkdown/md4c/md2html/cmdline.c create mode 100644 tdemarkdown/md4c/md2html/cmdline.h create mode 100644 tdemarkdown/md4c/md2html/md2html.1 create mode 100644 tdemarkdown/md4c/md2html/md2html.c create mode 100644 tdemarkdown/md4c/scripts/build_folding_map.py create mode 100644 tdemarkdown/md4c/scripts/build_punct_map.py create mode 100644 tdemarkdown/md4c/scripts/build_whitespace_map.py create mode 100755 tdemarkdown/md4c/scripts/coverity.sh create mode 100755 tdemarkdown/md4c/scripts/run-tests.sh create mode 100644 tdemarkdown/md4c/scripts/unicode/CaseFolding.txt create mode 100644 tdemarkdown/md4c/scripts/unicode/DerivedGeneralCategory.txt create mode 100644 tdemarkdown/md4c/src/CMakeLists.txt create mode 100644 tdemarkdown/md4c/src/entity.c create mode 100644 tdemarkdown/md4c/src/entity.h create mode 100644 tdemarkdown/md4c/src/md4c-html.c create mode 100644 tdemarkdown/md4c/src/md4c-html.h create mode 100644 tdemarkdown/md4c/src/md4c-html.pc.in create mode 100644 tdemarkdown/md4c/src/md4c.c create mode 100644 tdemarkdown/md4c/src/md4c.h create mode 100644 tdemarkdown/md4c/src/md4c.pc.in create mode 100644 tdemarkdown/md4c/test/LICENSE create mode 100755 tdemarkdown/md4c/test/cmark.py create mode 100644 tdemarkdown/md4c/test/coverage.txt create mode 100644 tdemarkdown/md4c/test/fuzz-input/commonmark.md create mode 100644 tdemarkdown/md4c/test/fuzz-input/gfm.md create mode 100644 tdemarkdown/md4c/test/fuzz-input/latex-math.md create mode 100644 tdemarkdown/md4c/test/fuzz-input/wiki.md create mode 100644 tdemarkdown/md4c/test/fuzzers/fuzz-mdhtml.c create mode 100644 tdemarkdown/md4c/test/latex-math.txt create mode 100755 tdemarkdown/md4c/test/normalize.py create mode 100755 tdemarkdown/md4c/test/pathological_tests.py create mode 100644 tdemarkdown/md4c/test/permissive-email-autolinks.txt create mode 100644 tdemarkdown/md4c/test/permissive-url-autolinks.txt create mode 100644 tdemarkdown/md4c/test/permissive-www-autolinks.txt create mode 100644 tdemarkdown/md4c/test/spec.txt create mode 100755 tdemarkdown/md4c/test/spec_tests.py create mode 100644 tdemarkdown/md4c/test/strikethrough.txt create mode 100644 tdemarkdown/md4c/test/tables.txt create mode 100644 tdemarkdown/md4c/test/tasklists.txt create mode 100644 tdemarkdown/md4c/test/underline.txt create mode 100644 tdemarkdown/md4c/test/wiki-links.txt create mode 100644 translations/desktop_files/tdemarkdown-desktops/tdemarkdown-desktops.pot diff --git a/CMakeL10n.txt b/CMakeL10n.txt index fdf5509d7..10427d1a0 100644 --- a/CMakeL10n.txt +++ b/CMakeL10n.txt @@ -120,6 +120,7 @@ tde_l10n_create_template( "^tdecore/tdeconfig_compiler/example/" "^tdeio/" "^tdeioslave/" + "^tdemarkdown/md4c/" "^tdeprint/" "^tdeui/colors/" "^tdestyles/.*/config/" diff --git a/CMakeLists.txt b/CMakeLists.txt index 612bc212d..db151f471 100644 --- a/CMakeLists.txt +++ b/CMakeLists.txt @@ -1363,6 +1363,7 @@ add_subdirectory( kate ) add_subdirectory( tdecert ) tde_conditional_add_subdirectory( WITH_XRANDR tderandr ) add_subdirectory( tdehtml ) +add_subdirectory( tdemarkdown ) add_subdirectory( tdecmshell ) add_subdirectory( tdeconf_update ) add_subdirectory( tdewidgets ) diff --git a/mimetypes/text/CMakeLists.txt b/mimetypes/text/CMakeLists.txt index 918024dce..7f815bf86 100644 --- a/mimetypes/text/CMakeLists.txt +++ b/mimetypes/text/CMakeLists.txt @@ -21,6 +21,7 @@ tde_create_translated_desktop( x-bibtex.desktop rdf.desktop rss.desktop calendar.desktop x-adasrc.desktop x-perl.desktop x-csv.desktop x-latex.desktop x-xslfo.desktop x-xslt.desktop vnd.wap.wml.desktop x-katefilelist.desktop docbook.desktop x-mswinurl.desktop x-hex.desktop vnd.abc.desktop javascript.desktop x-python.desktop + markdown.desktop DESTINATION ${MIME_INSTALL_DIR}/text PO_DIR mimetypes ) diff --git a/mimetypes/text/markdown.desktop b/mimetypes/text/markdown.desktop new file mode 100644 index 000000000..41719d086 --- /dev/null +++ b/mimetypes/text/markdown.desktop @@ -0,0 +1,11 @@ +[Desktop Entry] +Comment=Markdown document +Type=MimeType +MimeType=text/markdown +Icon=text-x-generic +Patterns=*.md; +DefaultApp=konqueror + +[Property::X-TDE-text] +Type=bool +Value=true diff --git a/tdemarkdown/CMakeL10n.txt b/tdemarkdown/CMakeL10n.txt new file mode 100644 index 000000000..89b0e07f9 --- /dev/null +++ b/tdemarkdown/CMakeL10n.txt @@ -0,0 +1,8 @@ +##### create translation templates ############## + +tde_l10n_create_template( + CATALOG "desktop_files/tdemarkdown-desktops/" + SOURCES *.desktop + EXCLUDES "^md4c/" + DESTINATION "${CMAKE_SOURCE_DIR}/translations" +) diff --git a/tdemarkdown/CMakeLists.txt b/tdemarkdown/CMakeLists.txt new file mode 100644 index 000000000..38df3b6e0 --- /dev/null +++ b/tdemarkdown/CMakeLists.txt @@ -0,0 +1,67 @@ +########################################### +# # +# Copyright (C) 2022 Mavridis Philippe # +# # +# # +# Improvements and feedback are welcome # +# # +# Released under GNU GPL v2 or greater. # +# # +########################################### + +### Header and library directories ######## +# +include_directories( + ${CMAKE_SOURCE_DIR} + ${CMAKE_BINARY_DIR} + ${CMAKE_SOURCE_DIR}/tdecore + ${CMAKE_BINARY_DIR}/tdecore + ${CMAKE_SOURCE_DIR}/tdehtml + ${CMAKE_SOURCE_DIR}/tdeui + ${CMAKE_SOURCE_DIR}/tdeutils + ${CMAKE_CURRENT_SOURCE_DIR} + ${CMAKE_CURRENT_BINARY_DIR} + ${CMAKE_CURRENT_SOURCE_DIR}/md4c/src +) + +include_directories( SYSTEM + ${TQT_INCLUDE_DIRS} + ${TDE_INCLUDE_DIR} +) + +link_directories( + ${TQT_LIBRARY_DIRS} + ${TDE_LIB_DIR} +) + + +### Build libtdemarkdown (kpart) ########### +# +tde_add_kpart( libtdemarkdown + AUTOMOC + SOURCES + ${CMAKE_CURRENT_SOURCE_DIR}/md4c/src/entity.c + ${CMAKE_CURRENT_SOURCE_DIR}/md4c/src/md4c.c + ${CMAKE_CURRENT_SOURCE_DIR}/md4c/src/md4c-html.c + markdown_part.cpp + LINK + tdeparts-shared tdehtml-shared + DESTINATION ${PLUGIN_INSTALL_DIR} +) + + +### Install part .desktop entry ############# +# +tde_create_translated_desktop( + SOURCE markdown_part.desktop + DESTINATION ${SERVICES_INSTALL_DIR} + PO_DIR tdemarkdown-desktops +) + + +### Install XML-GUI ######################### +# +install( + FILES markdown_part.rc + DESTINATION ${DATA_INSTALL_DIR}/tdemarkdown +) diff --git a/tdemarkdown/LICENSE b/tdemarkdown/LICENSE new file mode 100644 index 000000000..17cb28643 --- /dev/null +++ b/tdemarkdown/LICENSE @@ -0,0 +1,117 @@ +GNU GENERAL PUBLIC LICENSE +Version 2, June 1991 + +Copyright (C) 1989, 1991 Free Software Foundation, 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See the GNU General Public License for more details. + + You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. Also add information on how to contact you by electronic and paper mail. + +If the program is interactive, make it output a short notice like this when it starts in an interactive mode: + + Gnomovision version 69, Copyright (C) year name of author Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'. This is free software, and you are welcome to redistribute it under certain conditions; type `show c' for details. + +The hypothetical commands `show w' and `show c' should show the appropriate parts of the General Public License. Of course, the commands you use may be called something other than `show w' and `show c'; they could even be mouse-clicks or menu items--whatever suits your program. + +You should also get your employer (if you work as a programmer) or your school, if any, to sign a "copyright disclaimer" for the program, if necessary. Here is a sample; alter the names: + + Yoyodyne, Inc., hereby disclaims all copyright interest in the program `Gnomovision' (which makes passes at compilers) written by James Hacker. + +signature of Ty Coon, 1 April 1989 Ty Coon, President of Vice diff --git a/tdemarkdown/README.md b/tdemarkdown/README.md new file mode 100644 index 000000000..0b6e811bf --- /dev/null +++ b/tdemarkdown/README.md @@ -0,0 +1,14 @@ +# TDEMarkdown + +TDEMarkdown is a lightweight markdown viewer for Trinity based on the [md4c](https://www.github.com/mity/md4c) library and using TDEHTML for rendering its output. + +It integrates nicely into Konqueror and supports both Commonmark and GitHub markdown syntaxes. + + +## Contributing + +If you wish to contribute to TDEMarkdown: + +- You can **report a bug, request a feature or contribute code** via the [TDE Gitea Workspace (TGW)](https://mirror.git.trinitydesktop.org/gitea) + +- You can **contribute translations** via the [TDE Weblate Translation Workspace (TWTW)](https://mirror.git.trinitydesktop.org/weblate) diff --git a/tdemarkdown/markdown_part.cpp b/tdemarkdown/markdown_part.cpp new file mode 100644 index 000000000..d4b7fb810 --- /dev/null +++ b/tdemarkdown/markdown_part.cpp @@ -0,0 +1,133 @@ +/*************************************************************************** + * Markdown Viewer part * + * Copyright (c) 2022 Mavridis Philippe * + * * + * This program is free software; you can redistribute it and/or modify * + * it under the terms of the GNU General Public License as published by * + * the Free Software Foundation; either version 2 of the License, or * + * (at your option) any later version. * + ***************************************************************************/ + + +#include +#include + +#include +#include + +#include + +/* MD4C-HTML */ +#include + +#include "markdown_part.h" + + +typedef KParts::GenericFactory Factory; +K_EXPORT_COMPONENT_FACTORY(libtdemarkdown, Factory) + +MarkdownPart::MarkdownPart(TQWidget* parentWidget, const char* widgetName, + TQObject* parent, const char* name, const TQStringList& args) + : TDEHTMLPart(parentWidget, name = "TDEMarkdown") +{ + setInstance(Factory::instance()); + + /* Features */ + setJScriptEnabled(false); + setJavaEnabled(false); + setMetaRefreshEnabled(false); + setPluginsEnabled(false); + setAutoloadImages(true); + setXMLFile( locate("data", "libtdemarkdown/markdown_part.rc") ); +} + +MarkdownPart::~MarkdownPart() +{ +} + +TDEAboutData* MarkdownPart::createAboutData() +{ + TDEAboutData* aboutData = new TDEAboutData( + "tdemarkdown", I18N_NOOP("TDE Markdown Viewer"), "1.0", + I18N_NOOP("TDEMarkdown is an embeddable viewer for Markdown documents."), + TDEAboutData::License_GPL_V2, "© 2022 Mavridis Philippe" + ); + aboutData->addAuthor("Mavridis Philippe (blu.256)", I18N_NOOP("Developer"), "mavridisf@gmail.com"); + return aboutData; +} + +bool MarkdownPart::openURL(const KURL& u) +{ + if(u.isLocalFile()) + { + TQFile local(u.path()); + + if(!local.open(IO_ReadOnly)) + { + return false; + } + + TQByteArray data = local.readAll(); + + local.close(); + + if(!data.isNull()) + { + begin(u); + TQString parsed(parse((MD_CHAR*) data.data())); + write(parsed); + end(); + } + } + + emit started(0L); + return true; +} + +TQString& MarkdownPart::parse(MD_CHAR* document) +{ + m_buffer = "\n"; + m_buffer += "\n"; + m_buffer += " \n"; + m_buffer += " \n"; + m_buffer += " TODO\n"; + m_buffer += " \n"; + m_buffer += " \n"; + + TQByteArray data; + int success = md_html(document, + MD_SIZE(strlen(document)), + &MarkdownPart::processHTML, + &data, + MD_DIALECT_GITHUB | MD_FLAG_PERMISSIVEURLAUTOLINKS | MD_FLAG_PERMISSIVEEMAILAUTOLINKS | MD_FLAG_PERMISSIVEWWWAUTOLINKS + | MD_FLAG_LATEXMATHSPANS | MD_FLAG_PERMISSIVEATXHEADERS | MD_FLAG_UNDERLINE | MD_FLAG_TASKLISTS, + 0); + + if (success == -1) + { + m_buffer += TQString("%1").arg(i18n("Error: malformed document.")); + } + else + { + m_buffer += TQString::fromLocal8Bit(data); + } + + m_buffer += " \n"; + m_buffer += "\n"; + return m_buffer; +} + +void MarkdownPart::processHTML(const MD_CHAR* data, MD_SIZE data_size, void* user_data) +{ + TQByteArray *ud = static_cast(user_data); + TQBuffer buff(*ud); + + if (data_size > 0) + { + buff.open(IO_WriteOnly | IO_Append); + buff.writeBlock(data, (int)data_size); + buff.close(); + } +} + +#include "markdown_part.moc" diff --git a/tdemarkdown/markdown_part.desktop b/tdemarkdown/markdown_part.desktop new file mode 100644 index 000000000..47cff4b03 --- /dev/null +++ b/tdemarkdown/markdown_part.desktop @@ -0,0 +1,10 @@ +[Desktop Entry] +Name=Markdown Viewer + +Comment=Embeddable lightweight markdown viewing component + +Type=Service +Icon=text-x-generic +MimeType=text/markdown +X-TDE-Library=libtdemarkdown +X-TDE-ServiceTypes=KParts/ReadOnlyPart diff --git a/tdemarkdown/markdown_part.h b/tdemarkdown/markdown_part.h new file mode 100644 index 000000000..0131553d3 --- /dev/null +++ b/tdemarkdown/markdown_part.h @@ -0,0 +1,47 @@ +/*************************************************************************** + * Markdown Viewer part * + * Copyright (c) 2022 Mavridis Philippe * + * * + * This program is free software; you can redistribute it and/or modify * + * it under the terms of the GNU General Public License as published by * + * the Free Software Foundation; either version 2 of the License, or * + * (at your option) any later version. * + ***************************************************************************/ + + +#ifndef __MARKDOWN_PART_H +#define __MARKDOWN_PART_H + +#include + +#include + +class TDEHTMLPart; + +class MarkdownPart : public TDEHTMLPart +{ + TQ_OBJECT + + public: + MarkdownPart(TQWidget* parentWidget, const char* widgetName, + TQObject* parent, const char* name, const TQStringList& args); + ~MarkdownPart(); + + /* Create and return About data */ + static TDEAboutData* createAboutData(); + + /* Implemented virtual from TDEHTMLPart */ + bool openURL(const KURL& u); + + /* Parser */ + TQString& parse(MD_CHAR* document); + + private: + TQString m_buffer; + + static void processHTML(const MD_CHAR* data, MD_SIZE data_size, void* userData); + +}; + + +#endif // __MARKDOWN_PART_H diff --git a/tdemarkdown/markdown_part.rc b/tdemarkdown/markdown_part.rc new file mode 100644 index 000000000..437f7814d --- /dev/null +++ b/tdemarkdown/markdown_part.rc @@ -0,0 +1,4 @@ + + + + \ No newline at end of file diff --git a/tdemarkdown/md4c/CHANGELOG.md b/tdemarkdown/md4c/CHANGELOG.md new file mode 100644 index 000000000..63a9c3233 --- /dev/null +++ b/tdemarkdown/md4c/CHANGELOG.md @@ -0,0 +1,442 @@ + +# MD4C Change Log + + +## Next Version (Work in Progress) + +Changes: + + * Changes mandated by CommonMark specification 0.30. + + Actually there are only very minor changes to recognition of HTML blocks: + + - The tag `` (case-insensitive; it +need not match the start tag). + +2. **Start condition:** line begins with the string ``. + +3. **Start condition:** line begins with the string ``. + +4. **Start condition:** line begins with the string ``. + +5. **Start condition:** line begins with the string +``. + +6. **Start condition:** line begins the string `<` or ``, or +the string `/>`.\ +**End condition:** line is followed by a [blank line]. + +7. **Start condition:** line begins with a complete [open tag] +(with any [tag name] other than `pre`, `script`, +`style`, or `textarea`) or a complete [closing tag], +followed by zero or more spaces and tabs, followed by the end of the line.\ +**End condition:** line is followed by a [blank line]. + +HTML blocks continue until they are closed by their appropriate +[end condition], or the last line of the document or other [container +block](#container-blocks). This means any HTML **within an HTML +block** that might otherwise be recognised as a start condition will +be ignored by the parser and passed through as-is, without changing +the parser's state. + +For instance, `
` within an HTML block started by `` will not affect
+the parser state; as the HTML block was started in by start condition 6, it
+will end at any blank line. This can be surprising:
+
+```````````````````````````````` example
+

+
+**Hello**,
+
+_world_.
+

+

+.
+

+
+**Hello**,
+
world.
+

+

+````````````````````````````````
+
+In this case, the HTML block is terminated by the blank line — the `**Hello**`
+text remains verbatim — and regular parsing resumes, with a paragraph,
+emphasised `world` and inline and block HTML following.
+
+All types of [HTML blocks] except type 7 may interrupt
+a paragraph.  Blocks of type 7 may not interrupt a paragraph.
+(This restriction is intended to prevent unwanted interpretation
+of long tags inside a wrapped paragraph as starting HTML blocks.)
+
+Some simple examples follow.  Here are some basic HTML blocks
+of type 6:
+
+```````````````````````````````` example
+
+  
+    
+  
+

+           hi
+    

+
+okay.
+.
+
+  
+    
+  
+

+           hi
+    

+
okay.

+````````````````````````````````
+
+
+```````````````````````````````` example
+ 
+*foo*
+````````````````````````````````
+
+
+Here we have two HTML blocks with a Markdown paragraph between them:
+
+```````````````````````````````` example
+

+
+*Markdown*
+
+

+.
+

+
Markdown

+

+````````````````````````````````
+
+
+The tag on the first line can be partial, as long
+as it is split where there would be whitespace:
+
+```````````````````````````````` example
+

+

+.
+

+

+````````````````````````````````
+
+
+```````````````````````````````` example
+

+

+.
+

+

+````````````````````````````````
+
+
+An open tag need not be closed:
+```````````````````````````````` example
+

+*foo*
+
+*bar*
+.
+

+*foo*
+
bar

+````````````````````````````````
+
+
+
+A partial tag need not even be completed (garbage
+in, garbage out):
+
+```````````````````````````````` example
+
+.
+
+````````````````````````````````
+
+
+```````````````````````````````` example
+

+foo
+

+.
+

+foo
+

+````````````````````````````````
+
+
+Everything until the next blank line or end of document
+gets included in the HTML block.  So, in the following
+example, what looks like a Markdown code block
+is actually part of the HTML block, which continues until a blank
+line or the end of the document is reached:
+
+```````````````````````````````` example
+

+``` c
+int x = 33;
+```
+.
+

+``` c
+int x = 33;
+```
+````````````````````````````````
+
+
+To start an [HTML block] with a tag that is *not* in the
+list of block-level tags in (6), you must put the tag by
+itself on the first line (and it must be complete):
+
+```````````````````````````````` example
+
+*bar*
+
+.
+
+*bar*
+
+````````````````````````````````
+
+
+In type 7 blocks, the [tag name] can be anything:
+
+```````````````````````````````` example
+
+*bar*
+
+.
+
+*bar*
+
+````````````````````````````````
+
+
+```````````````````````````````` example
+
+*bar*
+
+.
+
+*bar*
+
+````````````````````````````````
+
+
+```````````````````````````````` example
+
+*bar*
+.
+
+*bar*
+````````````````````````````````
+
+
+These rules are designed to allow us to work with tags that
+can function as either block-level or inline-level tags.
+The `` tag is a nice example.  We can surround content with
+`` tags in three different ways.  In this case, we get a raw
+HTML block, because the `` tag is on a line by itself:
+
+```````````````````````````````` example
+
+*foo*
+
+.
+
+*foo*
+
+````````````````````````````````
+
+
+In this case, we get a raw HTML block that just includes
+the `` tag (because it ends with the following blank
+line).  So the contents get interpreted as CommonMark:
+
+```````````````````````````````` example
+
+
+*foo*
+
+
+.
+
+
foo

+
+````````````````````````````````
+
+
+Finally, in this case, the `` tags are interpreted
+as [raw HTML] *inside* the CommonMark paragraph.  (Because
+the tag is not on a line by itself, we get inline HTML
+rather than an [HTML block].)
+
+```````````````````````````````` example
+*foo*
+.
+
foo

+````````````````````````````````
+
+
+HTML tags designed to contain literal content
+(`pre`, `script`, `style`, `textarea`), comments, processing instructions,
+and declarations are treated somewhat differently.
+Instead of ending at the first blank line, these blocks
+end at the first line containing a corresponding end tag.
+As a result, these blocks can contain blank lines:
+
+A pre tag (type 1):
+
+```````````````````````````````` example
+

+import Text.HTML.TagSoup
+
+main :: IO ()
+main = print $ parseTags tags
+

+okay
+.
+

+import Text.HTML.TagSoup
+
+main :: IO ()
+main = print $ parseTags tags
+

+
okay

+````````````````````````````````
+
+
+A script tag (type 1):
+
+```````````````````````````````` example
+
+okay
+.
+
+
okay

+````````````````````````````````
+
+
+A textarea tag (type 1):
+
+```````````````````````````````` example
+
+.
+
+````````````````````````````````
+
+A style tag (type 1):
+
+```````````````````````````````` example
+
+okay
+.
+
+
okay

+````````````````````````````````
+
+
+If there is no matching end tag, the block will end at the
+end of the document (or the enclosing [block quote][block quotes]
+or [list item][list items]):
+
+```````````````````````````````` example
+
+*foo*
+.
+
+
foo

+````````````````````````````````
+
+
+```````````````````````````````` example
+*bar*
+*baz*
+.
+*bar*
+
baz

+````````````````````````````````
+
+
+Note that anything on the last line after the
+end tag will be included in the [HTML block]:
+
+```````````````````````````````` example
+1. *bar*
+.
+1. *bar*
+````````````````````````````````
+
+
+A comment (type 2):
+
+```````````````````````````````` example
+
+okay
+.
+
+
okay

+````````````````````````````````
+
+
+
+A processing instruction (type 3):
+
+```````````````````````````````` example
+';
+
+?>
+okay
+.
+';
+
+?>
+
okay

+````````````````````````````````
+
+
+A declaration (type 4):
+
+```````````````````````````````` example
+
+.
+
+````````````````````````````````
+
+
+CDATA (type 5):
+
+```````````````````````````````` example
+
+okay
+.
+
+
okay

+````````````````````````````````
+
+
+The opening tag can be preceded by up to three spaces of indentation, but not
+four:
+
+```````````````````````````````` example
+  
+
+    
+.
+  
+
<!-- foo -->
+

+````````````````````````````````
+
+
+```````````````````````````````` example
+  

+
+    

+.
+  

+
<div>
+

+````````````````````````````````
+
+
+An HTML block of types 1--6 can interrupt a paragraph, and need not be
+preceded by a blank line.
+
+```````````````````````````````` example
+Foo
+

+bar
+

+.
+
Foo

+

+bar
+

+````````````````````````````````
+
+
+However, a following blank line is needed, except at the end of
+a document, and except for blocks of types 1--5, [above][HTML
+block]:
+
+```````````````````````````````` example
+

+bar
+

+*foo*
+.
+

+bar
+

+*foo*
+````````````````````````````````
+
+
+HTML blocks of type 7 cannot interrupt a paragraph:
+
+```````````````````````````````` example
+Foo
+
+baz
+.
+
Foo
+
+baz

+````````````````````````````````
+
+
+This rule differs from John Gruber's original Markdown syntax
+specification, which says:
+
+> The only restrictions are that block-level HTML elements —
+> e.g. `
`, ``, `
`, `
`, etc. — must be separated from
+> surrounding content by blank lines, and the start and end tags of the
+> block should not be indented with spaces or tabs.
+
+In some ways Gruber's rule is more restrictive than the one given
+here:
+
+- It requires that an HTML block be preceded by a blank line.
+- It does not allow the start tag to be indented.
+- It requires a matching end tag, which it also does not allow to
+  be indented.
+
+Most Markdown implementations (including some of Gruber's own) do not
+respect all of these restrictions.
+
+There is one respect, however, in which Gruber's rule is more liberal
+than the one given here, since it allows blank lines to occur inside
+an HTML block.  There are two reasons for disallowing them here.
+First, it removes the need to parse balanced tags, which is
+expensive and can require backtracking from the end of the document
+if no matching end tag is found. Second, it provides a very simple
+and flexible way of including Markdown content inside HTML tags:
+simply separate the Markdown from the HTML using blank lines:
+
+Compare:
+
+```````````````````````````````` example
+

+
+*Emphasized* text.
+
+

+.
+

+
Emphasized text.

+

+````````````````````````````````
+
+
+```````````````````````````````` example
+

+*Emphasized* text.
+

+.
+

+*Emphasized* text.
+

+````````````````````````````````
+
+
+Some Markdown implementations have adopted a convention of
+interpreting content inside tags as text if the open tag has
+the attribute `markdown=1`.  The rule given above seems a simpler and
+more elegant way of achieving the same expressive power, which is also
+much simpler to parse.
+
+The main potential drawback is that one can no longer paste HTML
+blocks into Markdown documents with 100% reliability.  However,
+*in most cases* this will work fine, because the blank lines in
+HTML are usually followed by HTML block tags.  For example:
+
+```````````````````````````````` example
+

+
+
+
+
+
+
+
+

+Hi
+

+.
+
+
+
+
+

+Hi
+

+````````````````````````````````
+
+
+There are problems, however, if the inner tags are indented
+*and* separated by spaces, as then they will be interpreted as
+an indented code block:
+
+```````````````````````````````` example
+
+
+  
+
+    
+
+  
+
+

+      Hi
+    

+.
+
+  
+
<td>
+  Hi
+</td>
+

+  
+

+````````````````````````````````
+
+
+Fortunately, blank lines are usually not necessary and can be
+deleted.  The exception is inside `
` tags, but as described
+[above][HTML blocks], raw HTML blocks starting with `
`
+*can* contain blank lines.
+
+## Link reference definitions
+
+A [link reference definition](@)
+consists of a [link label], optionally preceded by up to three spaces of
+indentation, followed
+by a colon (`:`), optional spaces or tabs (including up to one
+[line ending]), a [link destination],
+optional spaces or tabs (including up to one
+[line ending]), and an optional [link
+title], which if it is present must be separated
+from the [link destination] by spaces or tabs.
+No further character may occur.
+
+A [link reference definition]
+does not correspond to a structural element of a document.  Instead, it
+defines a label which can be used in [reference links]
+and reference-style [images] elsewhere in the document.  [Link
+reference definitions] can come either before or after the links that use
+them.
+
+```````````````````````````````` example
+[foo]: /url "title"
+
+[foo]
+.
+
foo

+````````````````````````````````
+
+
+```````````````````````````````` example
+   [foo]: 
+      /url  
+           'the title'  
+
+[foo]
+.
+
foo

+````````````````````````````````
+
+
+```````````````````````````````` example
+[Foo*bar\]]:my_(url) 'title (with parens)'
+
+[Foo*bar\]]
+.
+
Foo*bar]

+````````````````````````````````
+
+
+```````````````````````````````` example
+[Foo bar]:
+
+'title'
+
+[Foo bar]
+.
+
Foo bar

+````````````````````````````````
+
+
+The title may extend over multiple lines:
+
+```````````````````````````````` example
+[foo]: /url '
+title
+line1
+line2
+'
+
+[foo]
+.
+
foo

+````````````````````````````````
+
+
+However, it may not contain a [blank line]:
+
+```````````````````````````````` example
+[foo]: /url 'title
+
+with blank line'
+
+[foo]
+.
+
[foo]: /url 'title

+
with blank line'

+
[foo]

+````````````````````````````````
+
+
+The title may be omitted:
+
+```````````````````````````````` example
+[foo]:
+/url
+
+[foo]
+.
+
foo

+````````````````````````````````
+
+
+The link destination may not be omitted:
+
+```````````````````````````````` example
+[foo]:
+
+[foo]
+.
+
[foo]:

+
[foo]

+````````````````````````````````
+
+ However, an empty link destination may be specified using
+ angle brackets:
+
+```````````````````````````````` example
+[foo]: <>
+
+[foo]
+.
+
foo

+````````````````````````````````
+
+The title must be separated from the link destination by
+spaces or tabs:
+
+```````````````````````````````` example
+[foo]: (baz)
+
+[foo]
+.
+
[foo]: (baz)

+
[foo]

+````````````````````````````````
+
+
+Both title and destination can contain backslash escapes
+and literal backslashes:
+
+```````````````````````````````` example
+[foo]: /url\bar\*baz "foo\"bar\baz"
+
+[foo]
+.
+
foo

+````````````````````````````````
+
+
+A link can come before its corresponding definition:
+
+```````````````````````````````` example
+[foo]
+
+[foo]: url
+.
+
foo

+````````````````````````````````
+
+
+If there are several matching definitions, the first one takes
+precedence:
+
+```````````````````````````````` example
+[foo]
+
+[foo]: first
+[foo]: second
+.
+
foo

+````````````````````````````````
+
+
+As noted in the section on [Links], matching of labels is
+case-insensitive (see [matches]).
+
+```````````````````````````````` example
+[FOO]: /url
+
+[Foo]
+.
+
Foo

+````````````````````````````````
+
+
+```````````````````````````````` example
+[ΑΓΩ]: /φου
+
+[αγω]
+.
+
αγω

+````````````````````````````````
+
+
+Whether something is a [link reference definition] is
+independent of whether the link reference it defines is
+used in the document.  Thus, for example, the following
+document contains just a link reference definition, and
+no visible content:
+
+```````````````````````````````` example
+[foo]: /url
+.
+````````````````````````````````
+
+
+Here is another one:
+
+```````````````````````````````` example
+[
+foo
+]: /url
+bar
+.
+
bar

+````````````````````````````````
+
+
+This is not a link reference definition, because there are
+characters other than spaces or tabs after the title:
+
+```````````````````````````````` example
+[foo]: /url "title" ok
+.
+
[foo]: /url "title" ok

+````````````````````````````````
+
+
+This is a link reference definition, but it has no title:
+
+```````````````````````````````` example
+[foo]: /url
+"title" ok
+.
+
"title" ok

+````````````````````````````````
+
+
+This is not a link reference definition, because it is indented
+four spaces:
+
+```````````````````````````````` example
+    [foo]: /url "title"
+
+[foo]
+.
+
[foo]: /url "title"
+

+
[foo]

+````````````````````````````````
+
+
+This is not a link reference definition, because it occurs inside
+a code block:
+
+```````````````````````````````` example
+```
+[foo]: /url
+```
+
+[foo]
+.
+
[foo]: /url
+

+
[foo]

+````````````````````````````````
+
+
+A [link reference definition] cannot interrupt a paragraph.
+
+```````````````````````````````` example
+Foo
+[bar]: /baz
+
+[bar]
+.
+
Foo
+[bar]: /baz

+
[bar]

+````````````````````````````````
+
+
+However, it can directly follow other block elements, such as headings
+and thematic breaks, and it need not be followed by a blank line.
+
+```````````````````````````````` example
+# [Foo]
+[foo]: /url
+> bar
+.
+
Foo

+

+
bar

+

+````````````````````````````````
+
+```````````````````````````````` example
+[foo]: /url
+bar
+===
+[foo]
+.
+
bar

+
foo

+````````````````````````````````
+
+```````````````````````````````` example
+[foo]: /url
+===
+[foo]
+.
+
===
+foo

+````````````````````````````````
+
+
+Several [link reference definitions]
+can occur one after another, without intervening blank lines.
+
+```````````````````````````````` example
+[foo]: /foo-url "foo"
+[bar]: /bar-url
+  "bar"
+[baz]: /baz-url
+
+[foo],
+[bar],
+[baz]
+.
+
foo,
+bar,
+baz

+````````````````````````````````
+
+
+[Link reference definitions] can occur
+inside block containers, like lists and block quotations.  They
+affect the entire document, not just the container in which they
+are defined:
+
+```````````````````````````````` example
+[foo]
+
+> [foo]: /url
+.
+
foo

+

+

+````````````````````````````````
+
+
+## Paragraphs
+
+A sequence of non-blank lines that cannot be interpreted as other
+kinds of blocks forms a [paragraph](@).
+The contents of the paragraph are the result of parsing the
+paragraph's raw content as inlines.  The paragraph's raw content
+is formed by concatenating the lines and removing initial and final
+spaces or tabs.
+
+A simple example with two paragraphs:
+
+```````````````````````````````` example
+aaa
+
+bbb
+.
+
aaa

+
bbb

+````````````````````````````````
+
+
+Paragraphs can contain multiple lines, but no blank lines:
+
+```````````````````````````````` example
+aaa
+bbb
+
+ccc
+ddd
+.
+
aaa
+bbb

+
ccc
+ddd

+````````````````````````````````
+
+
+Multiple blank lines between paragraphs have no effect:
+
+```````````````````````````````` example
+aaa
+
+
+bbb
+.
+
aaa

+
bbb

+````````````````````````````````
+
+
+Leading spaces or tabs are skipped:
+
+```````````````````````````````` example
+  aaa
+ bbb
+.
+
aaa
+bbb

+````````````````````````````````
+
+
+Lines after the first may be indented any amount, since indented
+code blocks cannot interrupt paragraphs.
+
+```````````````````````````````` example
+aaa
+             bbb
+                                       ccc
+.
+
aaa
+bbb
+ccc

+````````````````````````````````
+
+
+However, the first line may be preceded by up to three spaces of indentation.
+Four spaces of indentation is too many:
+
+```````````````````````````````` example
+   aaa
+bbb
+.
+
aaa
+bbb

+````````````````````````````````
+
+
+```````````````````````````````` example
+    aaa
+bbb
+.
+
aaa
+

+
bbb

+````````````````````````````````
+
+
+Final spaces or tabs are stripped before inline parsing, so a paragraph
+that ends with two or more spaces will not end with a [hard line
+break]:
+
+```````````````````````````````` example
+aaa     
+bbb     
+.
+
aaa

+bbb

+````````````````````````````````
+
+
+## Blank lines
+
+[Blank lines] between block-level elements are ignored,
+except for the role they play in determining whether a [list]
+is [tight] or [loose].
+
+Blank lines at the beginning and end of the document are also ignored.
+
+```````````````````````````````` example
+  
+
+aaa
+  
+
+# aaa
+
+  
+.
+
aaa

+
aaa

+````````````````````````````````
+
+
+
+# Container blocks
+
+A [container block](#container-blocks) is a block that has other
+blocks as its contents.  There are two basic kinds of container blocks:
+[block quotes] and [list items].
+[Lists] are meta-containers for [list items].
+
+We define the syntax for container blocks recursively.  The general
+form of the definition is:
+
+> If X is a sequence of blocks, then the result of
+> transforming X in such-and-such a way is a container of type Y
+> with these blocks as its content.
+
+So, we explain what counts as a block quote or list item by explaining
+how these can be *generated* from their contents. This should suffice
+to define the syntax, although it does not give a recipe for *parsing*
+these constructions.  (A recipe is provided below in the section entitled
+[A parsing strategy](#appendix-a-parsing-strategy).)
+
+## Block quotes
+
+A [block quote marker](@),
+optionally preceded by up to three spaces of indentation,
+consists of (a) the character `>` together with a following space of
+indentation, or (b) a single character `>` not followed by a space of
+indentation.
+
+The following rules define [block quotes]:
+
+1.  **Basic case.**  If a string of lines *Ls* constitute a sequence
+    of blocks *Bs*, then the result of prepending a [block quote
+    marker] to the beginning of each line in *Ls*
+    is a [block quote](#block-quotes) containing *Bs*.
+
+2.  **Laziness.**  If a string of lines *Ls* constitute a [block
+    quote](#block-quotes) with contents *Bs*, then the result of deleting
+    the initial [block quote marker] from one or
+    more lines in which the next character other than a space or tab after the
+    [block quote marker] is [paragraph continuation
+    text] is a block quote with *Bs* as its content.
+    [Paragraph continuation text](@) is text
+    that will be parsed as part of the content of a paragraph, but does
+    not occur at the beginning of the paragraph.
+
+3.  **Consecutiveness.**  A document cannot contain two [block
+    quotes] in a row unless there is a [blank line] between them.
+
+Nothing else counts as a [block quote](#block-quotes).
+
+Here is a simple example:
+
+```````````````````````````````` example
+> # Foo
+> bar
+> baz
+.
+

+
Foo

+
bar
+baz

+

+````````````````````````````````
+
+
+The space or tab after the `>` characters can be omitted:
+
+```````````````````````````````` example
+># Foo
+>bar
+> baz
+.
+

+
Foo

+
bar
+baz

+

+````````````````````````````````
+
+
+The `>` characters can be preceded by up to three spaces of indentation:
+
+```````````````````````````````` example
+   > # Foo
+   > bar
+ > baz
+.
+

+
Foo

+
bar
+baz

+

+````````````````````````````````
+
+
+Four spaces of indentation is too many:
+
+```````````````````````````````` example
+    > # Foo
+    > bar
+    > baz
+.
+
> # Foo
+> bar
+> baz
+

+````````````````````````````````
+
+
+The Laziness clause allows us to omit the `>` before
+[paragraph continuation text]:
+
+```````````````````````````````` example
+> # Foo
+> bar
+baz
+.
+

+
Foo

+
bar
+baz

+

+````````````````````````````````
+
+
+A block quote can contain some lazy and some non-lazy
+continuation lines:
+
+```````````````````````````````` example
+> bar
+baz
+> foo
+.
+

+
bar
+baz
+foo

+

+````````````````````````````````
+
+
+Laziness only applies to lines that would have been continuations of
+paragraphs had they been prepended with [block quote markers].
+For example, the `> ` cannot be omitted in the second line of
+
+``` markdown
+> foo
+> ---
+```
+
+without changing the meaning:
+
+```````````````````````````````` example
+> foo
+---
+.
+

+
foo

+

+

+````````````````````````````````
+
+
+Similarly, if we omit the `> ` in the second line of
+
+``` markdown
+> - foo
+> - bar
+```
+
+then the block quote ends after the first line:
+
+```````````````````````````````` example
+> - foo
+- bar
+.
+

+
    
+
  • foo
    • 
+

+

+
    
+
  • bar
    • 
+

+````````````````````````````````
+
+
+For the same reason, we can't omit the `> ` in front of
+subsequent lines of an indented or fenced code block:
+
+```````````````````````````````` example
+>     foo
+    bar
+.
+

+
foo
+

+

+
bar
+

+````````````````````````````````
+
+
+```````````````````````````````` example
+> ```
+foo
+```
+.
+

+

+

+
foo

+

+````````````````````````````````
+
+
+Note that in the following case, we have a [lazy
+continuation line]:
+
+```````````````````````````````` example
+> foo
+    - bar
+.
+

+
foo
+- bar

+

+````````````````````````````````
+
+
+To see why, note that in
+
+```markdown
+> foo
+>     - bar
+```
+
+the `- bar` is indented too far to start a list, and can't
+be an indented code block because indented code blocks cannot
+interrupt paragraphs, so it is [paragraph continuation text].
+
+A block quote can be empty:
+
+```````````````````````````````` example
+>
+.
+

+

+````````````````````````````````
+
+
+```````````````````````````````` example
+>
+>  
+> 
+.
+

+

+````````````````````````````````
+
+
+A block quote can have initial or final blank lines:
+
+```````````````````````````````` example
+>
+> foo
+>  
+.
+

+
foo

+

+````````````````````````````````
+
+
+A blank line always separates block quotes:
+
+```````````````````````````````` example
+> foo
+
+> bar
+.
+

+
foo

+

+

+
bar

+

+````````````````````````````````
+
+
+(Most current Markdown implementations, including John Gruber's
+original `Markdown.pl`, will parse this example as a single block quote
+with two paragraphs.  But it seems better to allow the author to decide
+whether two block quotes or one are wanted.)
+
+Consecutiveness means that if we put these block quotes together,
+we get a single block quote:
+
+```````````````````````````````` example
+> foo
+> bar
+.
+

+
foo
+bar

+

+````````````````````````````````
+
+
+To get a block quote with two paragraphs, use:
+
+```````````````````````````````` example
+> foo
+>
+> bar
+.
+

+
foo

+
bar

+

+````````````````````````````````
+
+
+Block quotes can interrupt paragraphs:
+
+```````````````````````````````` example
+foo
+> bar
+.
+
foo

+

+
bar

+

+````````````````````````````````
+
+
+In general, blank lines are not needed before or after block
+quotes:
+
+```````````````````````````````` example
+> aaa
+***
+> bbb
+.
+

+
aaa

+

+

+

+
bbb

+

+````````````````````````````````
+
+
+However, because of laziness, a blank line is needed between
+a block quote and a following paragraph:
+
+```````````````````````````````` example
+> bar
+baz
+.
+

+
bar
+baz

+

+````````````````````````````````
+
+
+```````````````````````````````` example
+> bar
+
+baz
+.
+

+
bar

+

+
baz

+````````````````````````````````
+
+
+```````````````````````````````` example
+> bar
+>
+baz
+.
+

+
bar

+

+
baz

+````````````````````````````````
+
+
+It is a consequence of the Laziness rule that any number
+of initial `>`s may be omitted on a continuation line of a
+nested block quote:
+
+```````````````````````````````` example
+> > > foo
+bar
+.
+

+

+

+
foo
+bar

+

+

+

+````````````````````````````````
+
+
+```````````````````````````````` example
+>>> foo
+> bar
+>>baz
+.
+

+

+

+
foo
+bar
+baz

+

+

+

+````````````````````````````````
+
+
+When including an indented code block in a block quote,
+remember that the [block quote marker] includes
+both the `>` and a following space of indentation.  So *five spaces* are needed
+after the `>`:
+
+```````````````````````````````` example
+>     code
+
+>    not code
+.
+

+
code
+

+

+

+
not code

+

+````````````````````````````````
+
+
+
+## List items
+
+A [list marker](@) is a
+[bullet list marker] or an [ordered list marker].
+
+A [bullet list marker](@)
+is a `-`, `+`, or `*` character.
+
+An [ordered list marker](@)
+is a sequence of 1--9 arabic digits (`0-9`), followed by either a
+`.` character or a `)` character.  (The reason for the length
+limit is that with 10 digits we start seeing integer overflows
+in some browsers.)
+
+The following rules define [list items]:
+
+1.  **Basic case.**  If a sequence of lines *Ls* constitute a sequence of
+    blocks *Bs* starting with a character other than a space or tab, and *M* is
+    a list marker of width *W* followed by 1 ≤ *N* ≤ 4 spaces of indentation,
+    then the result of prepending *M* and the following spaces to the first line
+    of Ls*, and indenting subsequent lines of *Ls* by *W + N* spaces, is a
+    list item with *Bs* as its contents.  The type of the list item
+    (bullet or ordered) is determined by the type of its list marker.
+    If the list item is ordered, then it is also assigned a start
+    number, based on the ordered list marker.
+
+    Exceptions:
+
+    1. When the first list item in a [list] interrupts
+       a paragraph---that is, when it starts on a line that would
+       otherwise count as [paragraph continuation text]---then (a)
+       the lines *Ls* must not begin with a blank line, and (b) if
+       the list item is ordered, the start number must be 1.
+    2. If any line is a [thematic break][thematic breaks] then
+       that line is not a list item.
+
+For example, let *Ls* be the lines
+
+```````````````````````````````` example
+A paragraph
+with two lines.
+
+    indented code
+
+> A block quote.
+.
+
A paragraph
+with two lines.

+
indented code
+

+

+
A block quote.

+

+````````````````````````````````
+
+
+And let *M* be the marker `1.`, and *N* = 2.  Then rule #1 says
+that the following is an ordered list item with start number 1,
+and the same contents as *Ls*:
+
+```````````````````````````````` example
+1.  A paragraph
+    with two lines.
+
+        indented code
+
+    > A block quote.
+.
+
    
+
  1. 
+
    A paragraph
+with two lines.
    
+
    indented code
+
    
+
    
+
    A block quote.
    
+
    
+
    2. 
+

+````````````````````````````````
+
+
+The most important thing to notice is that the position of
+the text after the list marker determines how much indentation
+is needed in subsequent blocks in the list item.  If the list
+marker takes up two spaces of indentation, and there are three spaces between
+the list marker and the next character other than a space or tab, then blocks
+must be indented five spaces in order to fall under the list
+item.
+
+Here are some examples showing how far content must be indented to be
+put under the list item:
+
+```````````````````````````````` example
+- one
+
+ two
+.
+
    
+
  • one
    • 
+

+
two

+````````````````````````````````
+
+
+```````````````````````````````` example
+- one
+
+  two
+.
+
    
+
  • 
+
    one
    
+
    two
    
+
    • 
+

+````````````````````````````````
+
+
+```````````````````````````````` example
+ -    one
+
+     two
+.
+
    
+
  • one
    • 
+

+
 two
+

+````````````````````````````````
+
+
+```````````````````````````````` example
+ -    one
+
+      two
+.
+
    
+
  • 
+
    one
    
+
    two
    
+
    • 
+

+````````````````````````````````
+
+
+It is tempting to think of this in terms of columns:  the continuation
+blocks must be indented at least to the column of the first character other than
+a space or tab after the list marker.  However, that is not quite right.
+The spaces of indentation after the list marker determine how much relative
+indentation is needed.  Which column this indentation reaches will depend on
+how the list item is embedded in other constructions, as shown by
+this example:
+
+```````````````````````````````` example
+   > > 1.  one
+>>
+>>     two
+.
+

+

+
    
+
  1. 
+
    one
    
+
    two
    
+
    2. 
+

+

+

+````````````````````````````````
+
+
+Here `two` occurs in the same column as the list marker `1.`,
+but is actually contained in the list item, because there is
+sufficient indentation after the last containing blockquote marker.
+
+The converse is also possible.  In the following example, the word `two`
+occurs far to the right of the initial text of the list item, `one`, but
+it is not considered part of the list item, because it is not indented
+far enough past the blockquote marker:
+
+```````````````````````````````` example
+>>- one
+>>
+  >  > two
+.
+

+

+
    
+
  • one
    • 
+

+
two

+

+

+````````````````````````````````
+
+
+Note that at least one space or tab is needed between the list marker and
+any following content, so these are not list items:
+
+```````````````````````````````` example
+-one
+
+2.two
+.
+
-one

+
2.two

+````````````````````````````````
+
+
+A list item may contain blocks that are separated by more than
+one blank line.
+
+```````````````````````````````` example
+- foo
+
+
+  bar
+.
+
    
+
  • 
+
    foo
    
+
    bar
    
+
    • 
+

+````````````````````````````````
+
+
+A list item may contain any kind of block:
+
+```````````````````````````````` example
+1.  foo
+
+    ```
+    bar
+    ```
+
+    baz
+
+    > bam
+.
+
    
+
  1. 
+
    foo
    
+
    bar
+
    
+
    baz
    
+
    
+
    bam
    
+
    
+
    2. 
+

+````````````````````````````````
+
+
+A list item that contains an indented code block will preserve
+empty lines within the code block verbatim.
+
+```````````````````````````````` example
+- Foo
+
+      bar
+
+
+      baz
+.
+
    
+
  • 
+
    Foo
    
+
    bar
+
+
+baz
+
    
+
    • 
+

+````````````````````````````````
+
+Note that ordered list start numbers must be nine digits or less:
+
+```````````````````````````````` example
+123456789. ok
+.
+
    
+
  1. ok
    2. 
+

+````````````````````````````````
+
+
+```````````````````````````````` example
+1234567890. not ok
+.
+
1234567890. not ok

+````````````````````````````````
+
+
+A start number may begin with 0s:
+
+```````````````````````````````` example
+0. ok
+.
+
    
+
  1. ok
    2. 
+

+````````````````````````````````
+
+
+```````````````````````````````` example
+003. ok
+.
+
    
+
  1. ok
    2. 
+

+````````````````````````````````
+
+
+A start number may not be negative:
+
+```````````````````````````````` example
+-1. not ok
+.
+
-1. not ok

+````````````````````````````````
+
+
+
+2.  **Item starting with indented code.**  If a sequence of lines *Ls*
+    constitute a sequence of blocks *Bs* starting with an indented code
+    block, and *M* is a list marker of width *W* followed by
+    one space of indentation, then the result of prepending *M* and the
+    following space to the first line of *Ls*, and indenting subsequent lines
+    of *Ls* by *W + 1* spaces, is a list item with *Bs* as its contents.
+    If a line is empty, then it need not be indented.  The type of the
+    list item (bullet or ordered) is determined by the type of its list
+    marker.  If the list item is ordered, then it is also assigned a
+    start number, based on the ordered list marker.
+
+An indented code block will have to be preceded by four spaces of indentation
+beyond the edge of the region where text will be included in the list item.
+In the following case that is 6 spaces:
+
+```````````````````````````````` example
+- foo
+
+      bar
+.
+
    
+
  • 
+
    foo
    
+
    bar
+
    
+
    • 
+

+````````````````````````````````
+
+
+And in this case it is 11 spaces:
+
+```````````````````````````````` example
+  10.  foo
+
+           bar
+.
+
    
+
  1. 
+
    foo
    
+
    bar
+
    
+
    2. 
+

+````````````````````````````````
+
+
+If the *first* block in the list item is an indented code block,
+then by rule #2, the contents must be preceded by *one* space of indentation
+after the list marker:
+
+```````````````````````````````` example
+    indented code
+
+paragraph
+
+    more code
+.
+
indented code
+

+
paragraph

+
more code
+

+````````````````````````````````
+
+
+```````````````````````````````` example
+1.     indented code
+
+   paragraph
+
+       more code
+.
+
    
+
  1. 
+
    indented code
+
    
+
    paragraph
    
+
    more code
+
    
+
    2. 
+

+````````````````````````````````
+
+
+Note that an additional space of indentation is interpreted as space
+inside the code block:
+
+```````````````````````````````` example
+1.      indented code
+
+   paragraph
+
+       more code
+.
+
    
+
  1. 
+
     indented code
+
    
+
    paragraph
    
+
    more code
+
    
+
    2. 
+

+````````````````````````````````
+
+
+Note that rules #1 and #2 only apply to two cases:  (a) cases
+in which the lines to be included in a list item begin with a
+characer other than a space or tab, and (b) cases in which
+they begin with an indented code
+block.  In a case like the following, where the first block begins with
+three spaces of indentation, the rules do not allow us to form a list item by
+indenting the whole thing and prepending a list marker:
+
+```````````````````````````````` example
+   foo
+
+bar
+.
+
foo

+
bar

+````````````````````````````````
+
+
+```````````````````````````````` example
+-    foo
+
+  bar
+.
+
    
+
  • foo
    • 
+

+
bar

+````````````````````````````````
+
+
+This is not a significant restriction, because when a block is preceded by up to
+three spaces of indentation, the indentation can always be removed without
+a change in interpretation, allowing rule #1 to be applied.  So, in
+the above case:
+
+```````````````````````````````` example
+-  foo
+
+   bar
+.
+
    
+
  • 
+
    foo
    
+
    bar
    
+
    • 
+

+````````````````````````````````
+
+
+3.  **Item starting with a blank line.**  If a sequence of lines *Ls*
+    starting with a single [blank line] constitute a (possibly empty)
+    sequence of blocks *Bs*, and *M* is a list marker of width *W*,
+    then the result of prepending *M* to the first line of *Ls*, and
+    preceding subsequent lines of *Ls* by *W + 1* spaces of indentation, is a
+    list item with *Bs* as its contents.
+    If a line is empty, then it need not be indented.  The type of the
+    list item (bullet or ordered) is determined by the type of its list
+    marker.  If the list item is ordered, then it is also assigned a
+    start number, based on the ordered list marker.
+
+Here are some list items that start with a blank line but are not empty:
+
+```````````````````````````````` example
+-
+  foo
+-
+  ```
+  bar
+  ```
+-
+      baz
+.
+
    
+
  • foo
    • 
+
  • 
+
    bar
+
    
+
    • 
+
  • 
+
    baz
+
    
+
    • 
+

+````````````````````````````````
+
+When the list item starts with a blank line, the number of spaces
+following the list marker doesn't change the required indentation:
+
+```````````````````````````````` example
+-   
+  foo
+.
+
    
+
  • foo
    • 
+

+````````````````````````````````
+
+
+A list item can begin with at most one blank line.
+In the following example, `foo` is not part of the list
+item:
+
+```````````````````````````````` example
+-
+
+  foo
+.
+
    
+
  • 
+

+
foo

+````````````````````````````````
+
+
+Here is an empty bullet list item:
+
+```````````````````````````````` example
+- foo
+-
+- bar
+.
+
    
+
  • foo
    • 
+
  • 
+
  • bar
    • 
+

+````````````````````````````````
+
+
+It does not matter whether there are spaces or tabs following the [list marker]:
+
+```````````````````````````````` example
+- foo
+-   
+- bar
+.
+
    
+
  • foo
    • 
+
  • 
+
  • bar
    • 
+

+````````````````````````````````
+
+
+Here is an empty ordered list item:
+
+```````````````````````````````` example
+1. foo
+2.
+3. bar
+.
+
    
+
  1. foo
    2. 
+
  2. 
+
  3. bar
    4. 
+

+````````````````````````````````
+
+
+A list may start or end with an empty list item:
+
+```````````````````````````````` example
+*
+.
+
    
+
  • 
+

+````````````````````````````````
+
+However, an empty list item cannot interrupt a paragraph:
+
+```````````````````````````````` example
+foo
+*
+
+foo
+1.
+.
+
foo
+*

+
foo
+1.

+````````````````````````````````
+
+
+4.  **Indentation.**  If a sequence of lines *Ls* constitutes a list item
+    according to rule #1, #2, or #3, then the result of preceding each line
+    of *Ls* by up to three spaces of indentation (the same for each line) also
+    constitutes a list item with the same contents and attributes.  If a line is
+    empty, then it need not be indented.
+
+Indented one space:
+
+```````````````````````````````` example
+ 1.  A paragraph
+     with two lines.
+
+         indented code
+
+     > A block quote.
+.
+
    
+
  1. 
+
    A paragraph
+with two lines.
    
+
    indented code
+
    
+
    
+
    A block quote.
    
+
    
+
    2. 
+

+````````````````````````````````
+
+
+Indented two spaces:
+
+```````````````````````````````` example
+  1.  A paragraph
+      with two lines.
+
+          indented code
+
+      > A block quote.
+.
+
    
+
  1. 
+
    A paragraph
+with two lines.
    
+
    indented code
+
    
+
    
+
    A block quote.
    
+
    
+
    2. 
+

+````````````````````````````````
+
+
+Indented three spaces:
+
+```````````````````````````````` example
+   1.  A paragraph
+       with two lines.
+
+           indented code
+
+       > A block quote.
+.
+
    
+
  1. 
+
    A paragraph
+with two lines.
    
+
    indented code
+
    
+
    
+
    A block quote.
    
+
    
+
    2. 
+

+````````````````````````````````
+
+
+Four spaces indent gives a code block:
+
+```````````````````````````````` example
+    1.  A paragraph
+        with two lines.
+
+            indented code
+
+        > A block quote.
+.
+
1.  A paragraph
+    with two lines.
+
+        indented code
+
+    > A block quote.
+

+````````````````````````````````
+
+
+
+5.  **Laziness.**  If a string of lines *Ls* constitute a [list
+    item](#list-items) with contents *Bs*, then the result of deleting
+    some or all of the indentation from one or more lines in which the
+    next character other than a space or tab after the indentation is
+    [paragraph continuation text] is a
+    list item with the same contents and attributes.  The unindented
+    lines are called
+    [lazy continuation line](@)s.
+
+Here is an example with [lazy continuation lines]:
+
+```````````````````````````````` example
+  1.  A paragraph
+with two lines.
+
+          indented code
+
+      > A block quote.
+.
+
    
+
  1. 
+
    A paragraph
+with two lines.
    
+
    indented code
+
    
+
    
+
    A block quote.
    
+
    
+
    2. 
+

+````````````````````````````````
+
+
+Indentation can be partially deleted:
+
+```````````````````````````````` example
+  1.  A paragraph
+    with two lines.
+.
+
    
+
  1. A paragraph
+with two lines.
    2. 
+

+````````````````````````````````
+
+
+These examples show how laziness can work in nested structures:
+
+```````````````````````````````` example
+> 1. > Blockquote
+continued here.
+.
+

+
    
+
  1. 
+
    
+
    Blockquote
+continued here.
    
+
    
+
    2. 
+

+

+````````````````````````````````
+
+
+```````````````````````````````` example
+> 1. > Blockquote
+> continued here.
+.
+

+
    
+
  1. 
+
    
+
    Blockquote
+continued here.
    
+
    
+
    2. 
+

+

+````````````````````````````````
+
+
+
+6.  **That's all.** Nothing that is not counted as a list item by rules
+    #1--5 counts as a [list item](#list-items).
+
+The rules for sublists follow from the general rules
+[above][List items].  A sublist must be indented the same number
+of spaces of indentation a paragraph would need to be in order to be included
+in the list item.
+
+So, in this case we need two spaces indent:
+
+```````````````````````````````` example
+- foo
+  - bar
+    - baz
+      - boo
+.
+
    
+
  • foo
+
      
+
    • bar
+
        
+
      • baz
+
          
+
        • boo
          • 
+
        
+
        • 
+
      
+
      • 
+
    
+
    • 
+

+````````````````````````````````
+
+
+One is not enough:
+
+```````````````````````````````` example
+- foo
+ - bar
+  - baz
+   - boo
+.
+
    
+
  • foo
    • 
+
  • bar
    • 
+
  • baz
    • 
+
  • boo
    • 
+

+````````````````````````````````
+
+
+Here we need four, because the list marker is wider:
+
+```````````````````````````````` example
+10) foo
+    - bar
+.
+
    
+
  1. foo
+
      
+
    • bar
      • 
+
    
+
    2. 
+

+````````````````````````````````
+
+
+Three is not enough:
+
+```````````````````````````````` example
+10) foo
+   - bar
+.
+
    
+
  1. foo
    2. 
+

+
    
+
  • bar
    • 
+

+````````````````````````````````
+
+
+A list may be the first block in a list item:
+
+```````````````````````````````` example
+- - foo
+.
+
    
+
  • 
+
      
+
    • foo
      • 
+
    
+
    • 
+

+````````````````````````````````
+
+
+```````````````````````````````` example
+1. - 2. foo
+.
+
    
+
  1. 
+
      
+
    • 
+
        
+
      1. foo
        2. 
+
      
+
      • 
+
    
+
    2. 
+

+````````````````````````````````
+
+
+A list item can contain a heading:
+
+```````````````````````````````` example
+- # Foo
+- Bar
+  ---
+  baz
+.
+
    
+
  • 
+
    Foo
    
+
    • 
+
  • 
+
    Bar
    
+baz
    • 
+

+````````````````````````````````
+
+
+### Motivation
+
+John Gruber's Markdown spec says the following about list items:
+
+1. "List markers typically start at the left margin, but may be indented
+   by up to three spaces. List markers must be followed by one or more
+   spaces or a tab."
+
+2. "To make lists look nice, you can wrap items with hanging indents....
+   But if you don't want to, you don't have to."
+
+3. "List items may consist of multiple paragraphs. Each subsequent
+   paragraph in a list item must be indented by either 4 spaces or one
+   tab."
+
+4. "It looks nice if you indent every line of the subsequent paragraphs,
+   but here again, Markdown will allow you to be lazy."
+
+5. "To put a blockquote within a list item, the blockquote's `>`
+   delimiters need to be indented."
+
+6. "To put a code block within a list item, the code block needs to be
+   indented twice — 8 spaces or two tabs."
+
+These rules specify that a paragraph under a list item must be indented
+four spaces (presumably, from the left margin, rather than the start of
+the list marker, but this is not said), and that code under a list item
+must be indented eight spaces instead of the usual four.  They also say
+that a block quote must be indented, but not by how much; however, the
+example given has four spaces indentation.  Although nothing is said
+about other kinds of block-level content, it is certainly reasonable to
+infer that *all* block elements under a list item, including other
+lists, must be indented four spaces.  This principle has been called the
+*four-space rule*.
+
+The four-space rule is clear and principled, and if the reference
+implementation `Markdown.pl` had followed it, it probably would have
+become the standard.  However, `Markdown.pl` allowed paragraphs and
+sublists to start with only two spaces indentation, at least on the
+outer level.  Worse, its behavior was inconsistent: a sublist of an
+outer-level list needed two spaces indentation, but a sublist of this
+sublist needed three spaces.  It is not surprising, then, that different
+implementations of Markdown have developed very different rules for
+determining what comes under a list item.  (Pandoc and python-Markdown,
+for example, stuck with Gruber's syntax description and the four-space
+rule, while discount, redcarpet, marked, PHP Markdown, and others
+followed `Markdown.pl`'s behavior more closely.)
+
+Unfortunately, given the divergences between implementations, there
+is no way to give a spec for list items that will be guaranteed not
+to break any existing documents.  However, the spec given here should
+correctly handle lists formatted with either the four-space rule or
+the more forgiving `Markdown.pl` behavior, provided they are laid out
+in a way that is natural for a human to read.
+
+The strategy here is to let the width and indentation of the list marker
+determine the indentation necessary for blocks to fall under the list
+item, rather than having a fixed and arbitrary number.  The writer can
+think of the body of the list item as a unit which gets indented to the
+right enough to fit the list marker (and any indentation on the list
+marker).  (The laziness rule, #5, then allows continuation lines to be
+unindented if needed.)
+
+This rule is superior, we claim, to any rule requiring a fixed level of
+indentation from the margin.  The four-space rule is clear but
+unnatural. It is quite unintuitive that
+
+``` markdown
+- foo
+
+  bar
+
+  - baz
+```
+
+should be parsed as two lists with an intervening paragraph,
+
+``` html
+
    
+
  • foo
    • 
+

+
bar

+
    
+
  • baz
    • 
+

+```
+
+as the four-space rule demands, rather than a single list,
+
+``` html
+
    
+
  • 
+
    foo
    
+
    bar
    
+
      
+
    • baz
      • 
+
    
+
    • 
+

+```
+
+The choice of four spaces is arbitrary.  It can be learned, but it is
+not likely to be guessed, and it trips up beginners regularly.
+
+Would it help to adopt a two-space rule?  The problem is that such
+a rule, together with the rule allowing up to three spaces of indentation for
+the initial list marker, allows text that is indented *less than* the
+original list marker to be included in the list item. For example,
+`Markdown.pl` parses
+
+``` markdown
+   - one
+
+  two
+```
+
+as a single list item, with `two` a continuation paragraph:
+
+``` html
+
    
+
  • 
+
    one
    
+
    two
    
+
    • 
+

+```
+
+and similarly
+
+``` markdown
+>   - one
+>
+>  two
+```
+
+as
+
+``` html
+

+
    
+
  • 
+
    one
    
+
    two
    
+
    • 
+

+

+```
+
+This is extremely unintuitive.
+
+Rather than requiring a fixed indent from the margin, we could require
+a fixed indent (say, two spaces, or even one space) from the list marker (which
+may itself be indented).  This proposal would remove the last anomaly
+discussed.  Unlike the spec presented above, it would count the following
+as a list item with a subparagraph, even though the paragraph `bar`
+is not indented as far as the first paragraph `foo`:
+
+``` markdown
+ 10. foo
+
+   bar  
+```
+
+Arguably this text does read like a list item with `bar` as a subparagraph,
+which may count in favor of the proposal.  However, on this proposal indented
+code would have to be indented six spaces after the list marker.  And this
+would break a lot of existing Markdown, which has the pattern:
+
+``` markdown
+1.  foo
+
+        indented code
+```
+
+where the code is indented eight spaces.  The spec above, by contrast, will
+parse this text as expected, since the code block's indentation is measured
+from the beginning of `foo`.
+
+The one case that needs special treatment is a list item that *starts*
+with indented code.  How much indentation is required in that case, since
+we don't have a "first paragraph" to measure from?  Rule #2 simply stipulates
+that in such cases, we require one space indentation from the list marker
+(and then the normal four spaces for the indented code).  This will match the
+four-space rule in cases where the list marker plus its initial indentation
+takes four spaces (a common case), but diverge in other cases.
+
+## Lists
+
+A [list](@) is a sequence of one or more
+list items [of the same type].  The list items
+may be separated by any number of blank lines.
+
+Two list items are [of the same type](@)
+if they begin with a [list marker] of the same type.
+Two list markers are of the
+same type if (a) they are bullet list markers using the same character
+(`-`, `+`, or `*`) or (b) they are ordered list numbers with the same
+delimiter (either `.` or `)`).
+
+A list is an [ordered list](@)
+if its constituent list items begin with
+[ordered list markers], and a
+[bullet list](@) if its constituent list
+items begin with [bullet list markers].
+
+The [start number](@)
+of an [ordered list] is determined by the list number of
+its initial list item.  The numbers of subsequent list items are
+disregarded.
+
+A list is [loose](@) if any of its constituent
+list items are separated by blank lines, or if any of its constituent
+list items directly contain two block-level elements with a blank line
+between them.  Otherwise a list is [tight](@).
+(The difference in HTML output is that paragraphs in a loose list are
+wrapped in `
` tags, while paragraphs in a tight list are not.)
+
+Changing the bullet or ordered list delimiter starts a new list:
+
+```````````````````````````````` example
+- foo
+- bar
++ baz
+.
+
    
+
  • foo
    • 
+
  • bar
    • 
+

+
    
+
  • baz
    • 
+

+````````````````````````````````
+
+
+```````````````````````````````` example
+1. foo
+2. bar
+3) baz
+.
+
    
+
  1. foo
    2. 
+
  2. bar
    3. 
+

+
    
+
  1. baz
    2. 
+

+````````````````````````````````
+
+
+In CommonMark, a list can interrupt a paragraph. That is,
+no blank line is needed to separate a paragraph from a following
+list:
+
+```````````````````````````````` example
+Foo
+- bar
+- baz
+.
+
Foo

+
    
+
  • bar
    • 
+
  • baz
    • 
+

+````````````````````````````````
+
+`Markdown.pl` does not allow this, through fear of triggering a list
+via a numeral in a hard-wrapped line:
+
+``` markdown
+The number of windows in my house is
+14.  The number of doors is 6.
+```
+
+Oddly, though, `Markdown.pl` *does* allow a blockquote to
+interrupt a paragraph, even though the same considerations might
+apply.
+
+In CommonMark, we do allow lists to interrupt paragraphs, for
+two reasons.  First, it is natural and not uncommon for people
+to start lists without blank lines:
+
+``` markdown
+I need to buy
+- new shoes
+- a coat
+- a plane ticket
+```
+
+Second, we are attracted to a
+
+> [principle of uniformity](@):
+> if a chunk of text has a certain
+> meaning, it will continue to have the same meaning when put into a
+> container block (such as a list item or blockquote).
+
+(Indeed, the spec for [list items] and [block quotes] presupposes
+this principle.) This principle implies that if
+
+``` markdown
+  * I need to buy
+    - new shoes
+    - a coat
+    - a plane ticket
+```
+
+is a list item containing a paragraph followed by a nested sublist,
+as all Markdown implementations agree it is (though the paragraph
+may be rendered without `
` tags, since the list is "tight"),
+then
+
+``` markdown
+I need to buy
+- new shoes
+- a coat
+- a plane ticket
+```
+
+by itself should be a paragraph followed by a nested sublist.
+
+Since it is well established Markdown practice to allow lists to
+interrupt paragraphs inside list items, the [principle of
+uniformity] requires us to allow this outside list items as
+well.  ([reStructuredText](http://docutils.sourceforge.net/rst.html)
+takes a different approach, requiring blank lines before lists
+even inside other list items.)
+
+In order to solve of unwanted lists in paragraphs with
+hard-wrapped numerals, we allow only lists starting with `1` to
+interrupt paragraphs.  Thus,
+
+```````````````````````````````` example
+The number of windows in my house is
+14.  The number of doors is 6.
+.
+
The number of windows in my house is
+14.  The number of doors is 6.

+````````````````````````````````
+
+We may still get an unintended result in cases like
+
+```````````````````````````````` example
+The number of windows in my house is
+1.  The number of doors is 6.
+.
+
The number of windows in my house is

+
    
+
  1. The number of doors is 6.
    2. 
+

+````````````````````````````````
+
+but this rule should prevent most spurious list captures.
+
+There can be any number of blank lines between items:
+
+```````````````````````````````` example
+- foo
+
+- bar
+
+
+- baz
+.
+
    
+
  • 
+
    foo
    
+
    • 
+
  • 
+
    bar
    
+
    • 
+
  • 
+
    baz
    
+
    • 
+

+````````````````````````````````
+
+```````````````````````````````` example
+- foo
+  - bar
+    - baz
+
+
+      bim
+.
+
    
+
  • foo
+
      
+
    • bar
+
        
+
      • 
+
        baz
        
+
        bim
        
+
        • 
+
      
+
      • 
+
    
+
    • 
+

+````````````````````````````````
+
+
+To separate consecutive lists of the same type, or to separate a
+list from an indented code block that would otherwise be parsed
+as a subparagraph of the final list item, you can insert a blank HTML
+comment:
+
+```````````````````````````````` example
+- foo
+- bar
+
+
+
+- baz
+- bim
+.
+
    
+
  • foo
    • 
+
  • bar
    • 
+

+
+
    
+
  • baz
    • 
+
  • bim
    • 
+

+````````````````````````````````
+
+
+```````````````````````````````` example
+-   foo
+
+    notcode
+
+-   foo
+
+
+
+    code
+.
+
    
+
  • 
+
    foo
    
+
    notcode
    
+
    • 
+
  • 
+
    foo
    
+
    • 
+

+
+
code
+

+````````````````````````````````
+
+
+List items need not be indented to the same level.  The following
+list items will be treated as items at the same list level,
+since none is indented enough to belong to the previous list
+item:
+
+```````````````````````````````` example
+- a
+ - b
+  - c
+   - d
+  - e
+ - f
+- g
+.
+
    
+
  • a
    • 
+
  • b
    • 
+
  • c
    • 
+
  • d
    • 
+
  • e
    • 
+
  • f
    • 
+
  • g
    • 
+

+````````````````````````````````
+
+
+```````````````````````````````` example
+1. a
+
+  2. b
+
+   3. c
+.
+
    
+
  1. 
+
    a
    
+
    2. 
+
  2. 
+
    b
    
+
    3. 
+
  3. 
+
    c
    
+
    4. 
+

+````````````````````````````````
+
+Note, however, that list items may not be preceded by more than
+three spaces of indentation.  Here `- e` is treated as a paragraph continuation
+line, because it is indented more than three spaces:
+
+```````````````````````````````` example
+- a
+ - b
+  - c
+   - d
+    - e
+.
+
    
+
  • a
    • 
+
  • b
    • 
+
  • c
    • 
+
  • d
+- e
    • 
+

+````````````````````````````````
+
+And here, `3. c` is treated as in indented code block,
+because it is indented four spaces and preceded by a
+blank line.
+
+```````````````````````````````` example
+1. a
+
+  2. b
+
+    3. c
+.
+
    
+
  1. 
+
    a
    
+
    2. 
+
  2. 
+
    b
    
+
    3. 
+

+
3. c
+

+````````````````````````````````
+
+
+This is a loose list, because there is a blank line between
+two of the list items:
+
+```````````````````````````````` example
+- a
+- b
+
+- c
+.
+
    
+
  • 
+
    a
    
+
    • 
+
  • 
+
    b
    
+
    • 
+
  • 
+
    c
    
+
    • 
+

+````````````````````````````````
+
+
+So is this, with a empty second item:
+
+```````````````````````````````` example
+* a
+*
+
+* c
+.
+
    
+
  • 
+
    a
    
+
    • 
+
  • 
+
  • 
+
    c
    
+
    • 
+

+````````````````````````````````
+
+
+These are loose lists, even though there are no blank lines between the items,
+because one of the items directly contains two block-level elements
+with a blank line between them:
+
+```````````````````````````````` example
+- a
+- b
+
+  c
+- d
+.
+
    
+
  • 
+
    a
    
+
    • 
+
  • 
+
    b
    
+
    c
    
+
    • 
+
  • 
+
    d
    
+
    • 
+

+````````````````````````````````
+
+
+```````````````````````````````` example
+- a
+- b
+
+  [ref]: /url
+- d
+.
+
    
+
  • 
+
    a
    
+
    • 
+
  • 
+
    b
    
+
    • 
+
  • 
+
    d
    
+
    • 
+

+````````````````````````````````
+
+
+This is a tight list, because the blank lines are in a code block:
+
+```````````````````````````````` example
+- a
+- ```
+  b
+
+
+  ```
+- c
+.
+
    
+
  • a
    • 
+
  • 
+
    b
+
+
+
    
+
    • 
+
  • c
    • 
+

+````````````````````````````````
+
+
+This is a tight list, because the blank line is between two
+paragraphs of a sublist.  So the sublist is loose while
+the outer list is tight:
+
+```````````````````````````````` example
+- a
+  - b
+
+    c
+- d
+.
+
    
+
  • a
+
      
+
    • 
+
      b
      
+
      c
      
+
      • 
+
    
+
    • 
+
  • d
    • 
+

+````````````````````````````````
+
+
+This is a tight list, because the blank line is inside the
+block quote:
+
+```````````````````````````````` example
+* a
+  > b
+  >
+* c
+.
+
    
+
  • a
+
    
+
    b
    
+
    
+
    • 
+
  • c
    • 
+

+````````````````````````````````
+
+
+This list is tight, because the consecutive block elements
+are not separated by blank lines:
+
+```````````````````````````````` example
+- a
+  > b
+  ```
+  c
+  ```
+- d
+.
+
    
+
  • a
+
    
+
    b
    
+
    
+
    c
+
    
+
    • 
+
  • d
    • 
+

+````````````````````````````````
+
+
+A single-paragraph list is tight:
+
+```````````````````````````````` example
+- a
+.
+
    
+
  • a
    • 
+

+````````````````````````````````
+
+
+```````````````````````````````` example
+- a
+  - b
+.
+
    
+
  • a
+
      
+
    • b
      • 
+
    
+
    • 
+

+````````````````````````````````
+
+
+This list is loose, because of the blank line between the
+two block elements in the list item:
+
+```````````````````````````````` example
+1. ```
+   foo
+   ```
+
+   bar
+.
+
    
+
  1. 
+
    foo
+
    
+
    bar
    
+
    2. 
+

+````````````````````````````````
+
+
+Here the outer list is loose, the inner list tight:
+
+```````````````````````````````` example
+* foo
+  * bar
+
+  baz
+.
+
    
+
  • 
+
    foo
    
+
      
+
    • bar
      • 
+
    
+
    baz
    
+
    • 
+

+````````````````````````````````
+
+
+```````````````````````````````` example
+- a
+  - b
+  - c
+
+- d
+  - e
+  - f
+.
+
    
+
  • 
+
    a
    
+
      
+
    • b
      • 
+
    • c
      • 
+
    
+
    • 
+
  • 
+
    d
    
+
      
+
    • e
      • 
+
    • f
      • 
+
    
+
    • 
+

+````````````````````````````````
+
+
+# Inlines
+
+Inlines are parsed sequentially from the beginning of the character
+stream to the end (left to right, in left-to-right languages).
+Thus, for example, in
+
+```````````````````````````````` example
+`hi`lo`
+.
+
hilo`

+````````````````````````````````
+
+`hi` is parsed as code, leaving the backtick at the end as a literal
+backtick.
+
+
+
+## Code spans
+
+A [backtick string](@)
+is a string of one or more backtick characters (`` ` ``) that is neither
+preceded nor followed by a backtick.
+
+A [code span](@) begins with a backtick string and ends with
+a backtick string of equal length.  The contents of the code span are
+the characters between these two backtick strings, normalized in the
+following ways:
+
+- First, [line endings] are converted to [spaces].
+- If the resulting string both begins *and* ends with a [space]
+  character, but does not consist entirely of [space]
+  characters, a single [space] character is removed from the
+  front and back.  This allows you to include code that begins
+  or ends with backtick characters, which must be separated by
+  whitespace from the opening or closing backtick strings.
+
+This is a simple code span:
+
+```````````````````````````````` example
+`foo`
+.
+
foo

+````````````````````````````````
+
+
+Here two backticks are used, because the code contains a backtick.
+This example also illustrates stripping of a single leading and
+trailing space:
+
+```````````````````````````````` example
+`` foo ` bar ``
+.
+
foo ` bar

+````````````````````````````````
+
+
+This example shows the motivation for stripping leading and trailing
+spaces:
+
+```````````````````````````````` example
+` `` `
+.
+
``

+````````````````````````````````
+
+Note that only *one* space is stripped:
+
+```````````````````````````````` example
+`  ``  `
+.
+
 `` 

+````````````````````````````````
+
+The stripping only happens if the space is on both
+sides of the string:
+
+```````````````````````````````` example
+` a`
+.
+
 a

+````````````````````````````````
+
+Only [spaces], and not [unicode whitespace] in general, are
+stripped in this way:
+
+```````````````````````````````` example
+` b `
+.
+
 b 

+````````````````````````````````
+
+No stripping occurs if the code span contains only spaces:
+
+```````````````````````````````` example
+` `
+`  `
+.
+
 
+  

+````````````````````````````````
+
+
+[Line endings] are treated like spaces:
+
+```````````````````````````````` example
+``
+foo
+bar  
+baz
+``
+.
+
foo bar   baz

+````````````````````````````````
+
+```````````````````````````````` example
+``
+foo 
+``
+.
+
foo 

+````````````````````````````````
+
+
+Interior spaces are not collapsed:
+
+```````````````````````````````` example
+`foo   bar 
+baz`
+.
+
foo   bar  baz

+````````````````````````````````
+
+Note that browsers will typically collapse consecutive spaces
+when rendering `` elements, so it is recommended that
+the following CSS be used:
+
+    code{white-space: pre-wrap;}
+
+
+Note that backslash escapes do not work in code spans. All backslashes
+are treated literally:
+
+```````````````````````````````` example
+`foo\`bar`
+.
+
foo\bar`

+````````````````````````````````
+
+
+Backslash escapes are never needed, because one can always choose a
+string of *n* backtick characters as delimiters, where the code does
+not contain any strings of exactly *n* backtick characters.
+
+```````````````````````````````` example
+``foo`bar``
+.
+
foo`bar

+````````````````````````````````
+
+```````````````````````````````` example
+` foo `` bar `
+.
+
foo `` bar

+````````````````````````````````
+
+
+Code span backticks have higher precedence than any other inline
+constructs except HTML tags and autolinks.  Thus, for example, this is
+not parsed as emphasized text, since the second `*` is part of a code
+span:
+
+```````````````````````````````` example
+*foo`*`
+.
+
*foo*

+````````````````````````````````
+
+
+And this is not parsed as a link:
+
+```````````````````````````````` example
+[not a `link](/foo`)
+.
+
[not a link](/foo)

+````````````````````````````````
+
+
+Code spans, HTML tags, and autolinks have the same precedence.
+Thus, this is code:
+
+```````````````````````````````` example
+``
+.
+
<a href="">`

+````````````````````````````````
+
+
+But this is an HTML tag:
+
+```````````````````````````````` example
+`
+.
+
`

+````````````````````````````````
+
+
+And this is code:
+
+```````````````````````````````` example
+``
+.
+
<http://foo.bar.baz>`

+````````````````````````````````
+
+
+But this is an autolink:
+
+```````````````````````````````` example
+`
+.
+
http://foo.bar.`baz`

+````````````````````````````````
+
+
+When a backtick string is not closed by a matching backtick string,
+we just have literal backticks:
+
+```````````````````````````````` example
+```foo``
+.
+
```foo``

+````````````````````````````````
+
+
+```````````````````````````````` example
+`foo
+.
+
`foo

+````````````````````````````````
+
+The following case also illustrates the need for opening and
+closing backtick strings to be equal in length:
+
+```````````````````````````````` example
+`foo``bar``
+.
+
`foobar

+````````````````````````````````
+
+
+## Emphasis and strong emphasis
+
+John Gruber's original [Markdown syntax
+description](http://daringfireball.net/projects/markdown/syntax#em) says:
+
+> Markdown treats asterisks (`*`) and underscores (`_`) as indicators of
+> emphasis. Text wrapped with one `*` or `_` will be wrapped with an HTML
+> `` tag; double `*`'s or `_`'s will be wrapped with an HTML ``
+> tag.
+
+This is enough for most users, but these rules leave much undecided,
+especially when it comes to nested emphasis.  The original
+`Markdown.pl` test suite makes it clear that triple `***` and
+`___` delimiters can be used for strong emphasis, and most
+implementations have also allowed the following patterns:
+
+``` markdown
+***strong emph***
+***strong** in emph*
+***emph* in strong**
+**in strong *emph***
+*in emph **strong***
+```
+
+The following patterns are less widely supported, but the intent
+is clear and they are useful (especially in contexts like bibliography
+entries):
+
+``` markdown
+*emph *with emph* in it*
+**strong **with strong** in it**
+```
+
+Many implementations have also restricted intraword emphasis to
+the `*` forms, to avoid unwanted emphasis in words containing
+internal underscores.  (It is best practice to put these in code
+spans, but users often do not.)
+
+``` markdown
+internal emphasis: foo*bar*baz
+no emphasis: foo_bar_baz
+```
+
+The rules given below capture all of these patterns, while allowing
+for efficient parsing strategies that do not backtrack.
+
+First, some definitions.  A [delimiter run](@) is either
+a sequence of one or more `*` characters that is not preceded or
+followed by a non-backslash-escaped `*` character, or a sequence
+of one or more `_` characters that is not preceded or followed by
+a non-backslash-escaped `_` character.
+
+A [left-flanking delimiter run](@) is
+a [delimiter run] that is (1) not followed by [Unicode whitespace],
+and either (2a) not followed by a [Unicode punctuation character], or
+(2b) followed by a [Unicode punctuation character] and
+preceded by [Unicode whitespace] or a [Unicode punctuation character].
+For purposes of this definition, the beginning and the end of
+the line count as Unicode whitespace.
+
+A [right-flanking delimiter run](@) is
+a [delimiter run] that is (1) not preceded by [Unicode whitespace],
+and either (2a) not preceded by a [Unicode punctuation character], or
+(2b) preceded by a [Unicode punctuation character] and
+followed by [Unicode whitespace] or a [Unicode punctuation character].
+For purposes of this definition, the beginning and the end of
+the line count as Unicode whitespace.
+
+Here are some examples of delimiter runs.
+
+  - left-flanking but not right-flanking:
+
+    ```
+    ***abc
+      _abc
+    **"abc"
+     _"abc"
+    ```
+
+  - right-flanking but not left-flanking:
+
+    ```
+     abc***
+     abc_
+    "abc"**
+    "abc"_
+    ```
+
+  - Both left and right-flanking:
+
+    ```
+     abc***def
+    "abc"_"def"
+    ```
+
+  - Neither left nor right-flanking:
+
+    ```
+    abc *** def
+    a _ b
+    ```
+
+(The idea of distinguishing left-flanking and right-flanking
+delimiter runs based on the character before and the character
+after comes from Roopesh Chander's
+[vfmd](http://www.vfmd.org/vfmd-spec/specification/#procedure-for-identifying-emphasis-tags).
+vfmd uses the terminology "emphasis indicator string" instead of "delimiter
+run," and its rules for distinguishing left- and right-flanking runs
+are a bit more complex than the ones given here.)
+
+The following rules define emphasis and strong emphasis:
+
+1.  A single `*` character [can open emphasis](@)
+    iff (if and only if) it is part of a [left-flanking delimiter run].
+
+2.  A single `_` character [can open emphasis] iff
+    it is part of a [left-flanking delimiter run]
+    and either (a) not part of a [right-flanking delimiter run]
+    or (b) part of a [right-flanking delimiter run]
+    preceded by a [Unicode punctuation character].
+
+3.  A single `*` character [can close emphasis](@)
+    iff it is part of a [right-flanking delimiter run].
+
+4.  A single `_` character [can close emphasis] iff
+    it is part of a [right-flanking delimiter run]
+    and either (a) not part of a [left-flanking delimiter run]
+    or (b) part of a [left-flanking delimiter run]
+    followed by a [Unicode punctuation character].
+
+5.  A double `**` [can open strong emphasis](@)
+    iff it is part of a [left-flanking delimiter run].
+
+6.  A double `__` [can open strong emphasis] iff
+    it is part of a [left-flanking delimiter run]
+    and either (a) not part of a [right-flanking delimiter run]
+    or (b) part of a [right-flanking delimiter run]
+    preceded by a [Unicode punctuation character].
+
+7.  A double `**` [can close strong emphasis](@)
+    iff it is part of a [right-flanking delimiter run].
+
+8.  A double `__` [can close strong emphasis] iff
+    it is part of a [right-flanking delimiter run]
+    and either (a) not part of a [left-flanking delimiter run]
+    or (b) part of a [left-flanking delimiter run]
+    followed by a [Unicode punctuation character].
+
+9.  Emphasis begins with a delimiter that [can open emphasis] and ends
+    with a delimiter that [can close emphasis], and that uses the same
+    character (`_` or `*`) as the opening delimiter.  The
+    opening and closing delimiters must belong to separate
+    [delimiter runs].  If one of the delimiters can both
+    open and close emphasis, then the sum of the lengths of the
+    delimiter runs containing the opening and closing delimiters
+    must not be a multiple of 3 unless both lengths are
+    multiples of 3.
+
+10. Strong emphasis begins with a delimiter that
+    [can open strong emphasis] and ends with a delimiter that
+    [can close strong emphasis], and that uses the same character
+    (`_` or `*`) as the opening delimiter.  The
+    opening and closing delimiters must belong to separate
+    [delimiter runs].  If one of the delimiters can both open
+    and close strong emphasis, then the sum of the lengths of
+    the delimiter runs containing the opening and closing
+    delimiters must not be a multiple of 3 unless both lengths
+    are multiples of 3.
+
+11. A literal `*` character cannot occur at the beginning or end of
+    `*`-delimited emphasis or `**`-delimited strong emphasis, unless it
+    is backslash-escaped.
+
+12. A literal `_` character cannot occur at the beginning or end of
+    `_`-delimited emphasis or `__`-delimited strong emphasis, unless it
+    is backslash-escaped.
+
+Where rules 1--12 above are compatible with multiple parsings,
+the following principles resolve ambiguity:
+
+13. The number of nestings should be minimized. Thus, for example,
+    an interpretation `...` is always preferred to
+    `...`.
+
+14. An interpretation `...` is always
+    preferred to `...`.
+
+15. When two potential emphasis or strong emphasis spans overlap,
+    so that the second begins before the first ends and ends after
+    the first ends, the first takes precedence. Thus, for example,
+    `*foo _bar* baz_` is parsed as `foo _bar baz_` rather
+    than `*foo bar* baz`.
+
+16. When there are two potential emphasis or strong emphasis spans
+    with the same closing delimiter, the shorter one (the one that
+    opens later) takes precedence. Thus, for example,
+    `**foo **bar baz**` is parsed as `**foo bar baz`
+    rather than `foo **bar baz`.
+
+17. Inline code spans, links, images, and HTML tags group more tightly
+    than emphasis.  So, when there is a choice between an interpretation
+    that contains one of these elements and one that does not, the
+    former always wins.  Thus, for example, `*[foo*](bar)` is
+    parsed as `*foo*` rather than as
+    `[foo](bar)`.
+
+These rules can be illustrated through a series of examples.
+
+Rule 1:
+
+```````````````````````````````` example
+*foo bar*
+.
+
foo bar

+````````````````````````````````
+
+
+This is not emphasis, because the opening `*` is followed by
+whitespace, and hence not part of a [left-flanking delimiter run]:
+
+```````````````````````````````` example
+a * foo bar*
+.
+
a * foo bar*

+````````````````````````````````
+
+
+This is not emphasis, because the opening `*` is preceded
+by an alphanumeric and followed by punctuation, and hence
+not part of a [left-flanking delimiter run]:
+
+```````````````````````````````` example
+a*"foo"*
+.
+
a*"foo"*

+````````````````````````````````
+
+
+Unicode nonbreaking spaces count as whitespace, too:
+
+```````````````````````````````` example
+* a *
+.
+
* a *

+````````````````````````````````
+
+
+Intraword emphasis with `*` is permitted:
+
+```````````````````````````````` example
+foo*bar*
+.
+
foobar

+````````````````````````````````
+
+
+```````````````````````````````` example
+5*6*78
+.
+
5678

+````````````````````````````````
+
+
+Rule 2:
+
+```````````````````````````````` example
+_foo bar_
+.
+
foo bar

+````````````````````````````````
+
+
+This is not emphasis, because the opening `_` is followed by
+whitespace:
+
+```````````````````````````````` example
+_ foo bar_
+.
+
_ foo bar_

+````````````````````````````````
+
+
+This is not emphasis, because the opening `_` is preceded
+by an alphanumeric and followed by punctuation:
+
+```````````````````````````````` example
+a_"foo"_
+.
+
a_"foo"_

+````````````````````````````````
+
+
+Emphasis with `_` is not allowed inside words:
+
+```````````````````````````````` example
+foo_bar_
+.
+
foo_bar_

+````````````````````````````````
+
+
+```````````````````````````````` example
+5_6_78
+.
+
5_6_78

+````````````````````````````````
+
+
+```````````````````````````````` example
+пристаням_стремятся_
+.
+
пристаням_стремятся_

+````````````````````````````````
+
+
+Here `_` does not generate emphasis, because the first delimiter run
+is right-flanking and the second left-flanking:
+
+```````````````````````````````` example
+aa_"bb"_cc
+.
+
aa_"bb"_cc

+````````````````````````````````
+
+
+This is emphasis, even though the opening delimiter is
+both left- and right-flanking, because it is preceded by
+punctuation:
+
+```````````````````````````````` example
+foo-_(bar)_
+.
+
foo-(bar)

+````````````````````````````````
+
+
+Rule 3:
+
+This is not emphasis, because the closing delimiter does
+not match the opening delimiter:
+
+```````````````````````````````` example
+_foo*
+.
+
_foo*

+````````````````````````````````
+
+
+This is not emphasis, because the closing `*` is preceded by
+whitespace:
+
+```````````````````````````````` example
+*foo bar *
+.
+
*foo bar *

+````````````````````````````````
+
+
+A line ending also counts as whitespace:
+
+```````````````````````````````` example
+*foo bar
+*
+.
+
*foo bar
+*

+````````````````````````````````
+
+
+This is not emphasis, because the second `*` is
+preceded by punctuation and followed by an alphanumeric
+(hence it is not part of a [right-flanking delimiter run]:
+
+```````````````````````````````` example
+*(*foo)
+.
+
*(*foo)

+````````````````````````````````
+
+
+The point of this restriction is more easily appreciated
+with this example:
+
+```````````````````````````````` example
+*(*foo*)*
+.
+
(foo)

+````````````````````````````````
+
+
+Intraword emphasis with `*` is allowed:
+
+```````````````````````````````` example
+*foo*bar
+.
+
foobar

+````````````````````````````````
+
+
+
+Rule 4:
+
+This is not emphasis, because the closing `_` is preceded by
+whitespace:
+
+```````````````````````````````` example
+_foo bar _
+.
+
_foo bar _

+````````````````````````````````
+
+
+This is not emphasis, because the second `_` is
+preceded by punctuation and followed by an alphanumeric:
+
+```````````````````````````````` example
+_(_foo)
+.
+
_(_foo)

+````````````````````````````````
+
+
+This is emphasis within emphasis:
+
+```````````````````````````````` example
+_(_foo_)_
+.
+
(foo)

+````````````````````````````````
+
+
+Intraword emphasis is disallowed for `_`:
+
+```````````````````````````````` example
+_foo_bar
+.
+
_foo_bar

+````````````````````````````````
+
+
+```````````````````````````````` example
+_пристаням_стремятся
+.
+
_пристаням_стремятся

+````````````````````````````````
+
+
+```````````````````````````````` example
+_foo_bar_baz_
+.
+
foo_bar_baz

+````````````````````````````````
+
+
+This is emphasis, even though the closing delimiter is
+both left- and right-flanking, because it is followed by
+punctuation:
+
+```````````````````````````````` example
+_(bar)_.
+.
+
(bar).

+````````````````````````````````
+
+
+Rule 5:
+
+```````````````````````````````` example
+**foo bar**
+.
+
foo bar

+````````````````````````````````
+
+
+This is not strong emphasis, because the opening delimiter is
+followed by whitespace:
+
+```````````````````````````````` example
+** foo bar**
+.
+
** foo bar**

+````````````````````````````````
+
+
+This is not strong emphasis, because the opening `**` is preceded
+by an alphanumeric and followed by punctuation, and hence
+not part of a [left-flanking delimiter run]:
+
+```````````````````````````````` example
+a**"foo"**
+.
+
a**"foo"**

+````````````````````````````````
+
+
+Intraword strong emphasis with `**` is permitted:
+
+```````````````````````````````` example
+foo**bar**
+.
+
foobar

+````````````````````````````````
+
+
+Rule 6:
+
+```````````````````````````````` example
+__foo bar__
+.
+
foo bar

+````````````````````````````````
+
+
+This is not strong emphasis, because the opening delimiter is
+followed by whitespace:
+
+```````````````````````````````` example
+__ foo bar__
+.
+
__ foo bar__

+````````````````````````````````
+
+
+A line ending counts as whitespace:
+```````````````````````````````` example
+__
+foo bar__
+.
+
__
+foo bar__

+````````````````````````````````
+
+
+This is not strong emphasis, because the opening `__` is preceded
+by an alphanumeric and followed by punctuation:
+
+```````````````````````````````` example
+a__"foo"__
+.
+
a__"foo"__

+````````````````````````````````
+
+
+Intraword strong emphasis is forbidden with `__`:
+
+```````````````````````````````` example
+foo__bar__
+.
+
foo__bar__

+````````````````````````````````
+
+
+```````````````````````````````` example
+5__6__78
+.
+
5__6__78

+````````````````````````````````
+
+
+```````````````````````````````` example
+пристаням__стремятся__
+.
+
пристаням__стремятся__

+````````````````````````````````
+
+
+```````````````````````````````` example
+__foo, __bar__, baz__
+.
+
foo, bar, baz

+````````````````````````````````
+
+
+This is strong emphasis, even though the opening delimiter is
+both left- and right-flanking, because it is preceded by
+punctuation:
+
+```````````````````````````````` example
+foo-__(bar)__
+.
+
foo-(bar)

+````````````````````````````````
+
+
+
+Rule 7:
+
+This is not strong emphasis, because the closing delimiter is preceded
+by whitespace:
+
+```````````````````````````````` example
+**foo bar **
+.
+
**foo bar **

+````````````````````````````````
+
+
+(Nor can it be interpreted as an emphasized `*foo bar *`, because of
+Rule 11.)
+
+This is not strong emphasis, because the second `**` is
+preceded by punctuation and followed by an alphanumeric:
+
+```````````````````````````````` example
+**(**foo)
+.
+
**(**foo)

+````````````````````````````````
+
+
+The point of this restriction is more easily appreciated
+with these examples:
+
+```````````````````````````````` example
+*(**foo**)*
+.
+
(foo)

+````````````````````````````````
+
+
+```````````````````````````````` example
+**Gomphocarpus (*Gomphocarpus physocarpus*, syn.
+*Asclepias physocarpa*)**
+.
+
Gomphocarpus (Gomphocarpus physocarpus, syn.
+Asclepias physocarpa)

+````````````````````````````````
+
+
+```````````````````````````````` example
+**foo "*bar*" foo**
+.
+
foo "bar" foo

+````````````````````````````````
+
+
+Intraword emphasis:
+
+```````````````````````````````` example
+**foo**bar
+.
+
foobar

+````````````````````````````````
+
+
+Rule 8:
+
+This is not strong emphasis, because the closing delimiter is
+preceded by whitespace:
+
+```````````````````````````````` example
+__foo bar __
+.
+
__foo bar __

+````````````````````````````````
+
+
+This is not strong emphasis, because the second `__` is
+preceded by punctuation and followed by an alphanumeric:
+
+```````````````````````````````` example
+__(__foo)
+.
+
__(__foo)

+````````````````````````````````
+
+
+The point of this restriction is more easily appreciated
+with this example:
+
+```````````````````````````````` example
+_(__foo__)_
+.
+
(foo)

+````````````````````````````````
+
+
+Intraword strong emphasis is forbidden with `__`:
+
+```````````````````````````````` example
+__foo__bar
+.
+
__foo__bar

+````````````````````````````````
+
+
+```````````````````````````````` example
+__пристаням__стремятся
+.
+
__пристаням__стремятся

+````````````````````````````````
+
+
+```````````````````````````````` example
+__foo__bar__baz__
+.
+
foo__bar__baz

+````````````````````````````````
+
+
+This is strong emphasis, even though the closing delimiter is
+both left- and right-flanking, because it is followed by
+punctuation:
+
+```````````````````````````````` example
+__(bar)__.
+.
+
(bar).

+````````````````````````````````
+
+
+Rule 9:
+
+Any nonempty sequence of inline elements can be the contents of an
+emphasized span.
+
+```````````````````````````````` example
+*foo [bar](/url)*
+.
+
foo bar

+````````````````````````````````
+
+
+```````````````````````````````` example
+*foo
+bar*
+.
+
foo
+bar

+````````````````````````````````
+
+
+In particular, emphasis and strong emphasis can be nested
+inside emphasis:
+
+```````````````````````````````` example
+_foo __bar__ baz_
+.
+
foo bar baz

+````````````````````````````````
+
+
+```````````````````````````````` example
+_foo _bar_ baz_
+.
+
foo bar baz

+````````````````````````````````
+
+
+```````````````````````````````` example
+__foo_ bar_
+.
+
foo bar

+````````````````````````````````
+
+
+```````````````````````````````` example
+*foo *bar**
+.
+
foo bar

+````````````````````````````````
+
+
+```````````````````````````````` example
+*foo **bar** baz*
+.
+
foo bar baz

+````````````````````````````````
+
+```````````````````````````````` example
+*foo**bar**baz*
+.
+
foobarbaz

+````````````````````````````````
+
+Note that in the preceding case, the interpretation
+
+``` markdown
+
foobarbaz

+```
+
+
+is precluded by the condition that a delimiter that
+can both open and close (like the `*` after `foo`)
+cannot form emphasis if the sum of the lengths of
+the delimiter runs containing the opening and
+closing delimiters is a multiple of 3 unless
+both lengths are multiples of 3.
+
+
+For the same reason, we don't get two consecutive
+emphasis sections in this example:
+
+```````````````````````````````` example
+*foo**bar*
+.
+
foo**bar

+````````````````````````````````
+
+
+The same condition ensures that the following
+cases are all strong emphasis nested inside
+emphasis, even when the interior whitespace is
+omitted:
+
+
+```````````````````````````````` example
+***foo** bar*
+.
+
foo bar

+````````````````````````````````
+
+
+```````````````````````````````` example
+*foo **bar***
+.
+
foo bar

+````````````````````````````````
+
+
+```````````````````````````````` example
+*foo**bar***
+.
+
foobar

+````````````````````````````````
+
+
+When the lengths of the interior closing and opening
+delimiter runs are *both* multiples of 3, though,
+they can match to create emphasis:
+
+```````````````````````````````` example
+foo***bar***baz
+.
+
foobarbaz

+````````````````````````````````
+
+```````````````````````````````` example
+foo******bar*********baz
+.
+
foobar***baz

+````````````````````````````````
+
+
+Indefinite levels of nesting are possible:
+
+```````````````````````````````` example
+*foo **bar *baz* bim** bop*
+.
+
foo bar baz bim bop

+````````````````````````````````
+
+
+```````````````````````````````` example
+*foo [*bar*](/url)*
+.
+
foo bar

+````````````````````````````````
+
+
+There can be no empty emphasis or strong emphasis:
+
+```````````````````````````````` example
+** is not an empty emphasis
+.
+
** is not an empty emphasis

+````````````````````````````````
+
+
+```````````````````````````````` example
+**** is not an empty strong emphasis
+.
+
**** is not an empty strong emphasis

+````````````````````````````````
+
+
+
+Rule 10:
+
+Any nonempty sequence of inline elements can be the contents of an
+strongly emphasized span.
+
+```````````````````````````````` example
+**foo [bar](/url)**
+.
+
foo bar

+````````````````````````````````
+
+
+```````````````````````````````` example
+**foo
+bar**
+.
+
foo
+bar

+````````````````````````````````
+
+
+In particular, emphasis and strong emphasis can be nested
+inside strong emphasis:
+
+```````````````````````````````` example
+__foo _bar_ baz__
+.
+
foo bar baz

+````````````````````````````````
+
+
+```````````````````````````````` example
+__foo __bar__ baz__
+.
+
foo bar baz

+````````````````````````````````
+
+
+```````````````````````````````` example
+____foo__ bar__
+.
+
foo bar

+````````````````````````````````
+
+
+```````````````````````````````` example
+**foo **bar****
+.
+
foo bar

+````````````````````````````````
+
+
+```````````````````````````````` example
+**foo *bar* baz**
+.
+
foo bar baz

+````````````````````````````````
+
+
+```````````````````````````````` example
+**foo*bar*baz**
+.
+
foobarbaz

+````````````````````````````````
+
+
+```````````````````````````````` example
+***foo* bar**
+.
+
foo bar

+````````````````````````````````
+
+
+```````````````````````````````` example
+**foo *bar***
+.
+
foo bar

+````````````````````````````````
+
+
+Indefinite levels of nesting are possible:
+
+```````````````````````````````` example
+**foo *bar **baz**
+bim* bop**
+.
+
foo bar baz
+bim bop

+````````````````````````````````
+
+
+```````````````````````````````` example
+**foo [*bar*](/url)**
+.
+
foo bar

+````````````````````````````````
+
+
+There can be no empty emphasis or strong emphasis:
+
+```````````````````````````````` example
+__ is not an empty emphasis
+.
+
__ is not an empty emphasis

+````````````````````````````````
+
+
+```````````````````````````````` example
+____ is not an empty strong emphasis
+.
+
____ is not an empty strong emphasis

+````````````````````````````````
+
+
+
+Rule 11:
+
+```````````````````````````````` example
+foo ***
+.
+
foo ***

+````````````````````````````````
+
+
+```````````````````````````````` example
+foo *\**
+.
+
foo *

+````````````````````````````````
+
+
+```````````````````````````````` example
+foo *_*
+.
+
foo _

+````````````````````````````````
+
+
+```````````````````````````````` example
+foo *****
+.
+
foo *****

+````````````````````````````````
+
+
+```````````````````````````````` example
+foo **\***
+.
+
foo *

+````````````````````````````````
+
+
+```````````````````````````````` example
+foo **_**
+.
+
foo _

+````````````````````````````````
+
+
+Note that when delimiters do not match evenly, Rule 11 determines
+that the excess literal `*` characters will appear outside of the
+emphasis, rather than inside it:
+
+```````````````````````````````` example
+**foo*
+.
+
*foo

+````````````````````````````````
+
+
+```````````````````````````````` example
+*foo**
+.
+
foo*

+````````````````````````````````
+
+
+```````````````````````````````` example
+***foo**
+.
+
*foo

+````````````````````````````````
+
+
+```````````````````````````````` example
+****foo*
+.
+
***foo

+````````````````````````````````
+
+
+```````````````````````````````` example
+**foo***
+.
+
foo*

+````````````````````````````````
+
+
+```````````````````````````````` example
+*foo****
+.
+
foo***

+````````````````````````````````
+
+
+
+Rule 12:
+
+```````````````````````````````` example
+foo ___
+.
+
foo ___

+````````````````````````````````
+
+
+```````````````````````````````` example
+foo _\__
+.
+
foo _

+````````````````````````````````
+
+
+```````````````````````````````` example
+foo _*_
+.
+
foo *

+````````````````````````````````
+
+
+```````````````````````````````` example
+foo _____
+.
+
foo _____

+````````````````````````````````
+
+
+```````````````````````````````` example
+foo __\___
+.
+
foo _

+````````````````````````````````
+
+
+```````````````````````````````` example
+foo __*__
+.
+
foo *

+````````````````````````````````
+
+
+```````````````````````````````` example
+__foo_
+.
+
_foo

+````````````````````````````````
+
+
+Note that when delimiters do not match evenly, Rule 12 determines
+that the excess literal `_` characters will appear outside of the
+emphasis, rather than inside it:
+
+```````````````````````````````` example
+_foo__
+.
+
foo_

+````````````````````````````````
+
+
+```````````````````````````````` example
+___foo__
+.
+
_foo

+````````````````````````````````
+
+
+```````````````````````````````` example
+____foo_
+.
+
___foo

+````````````````````````````````
+
+
+```````````````````````````````` example
+__foo___
+.
+
foo_

+````````````````````````````````
+
+
+```````````````````````````````` example
+_foo____
+.
+
foo___

+````````````````````````````````
+
+
+Rule 13 implies that if you want emphasis nested directly inside
+emphasis, you must use different delimiters:
+
+```````````````````````````````` example
+**foo**
+.
+
foo

+````````````````````````````````
+
+
+```````````````````````````````` example
+*_foo_*
+.
+
foo

+````````````````````````````````
+
+
+```````````````````````````````` example
+__foo__
+.
+
foo

+````````````````````````````````
+
+
+```````````````````````````````` example
+_*foo*_
+.
+
foo

+````````````````````````````````
+
+
+However, strong emphasis within strong emphasis is possible without
+switching delimiters:
+
+```````````````````````````````` example
+****foo****
+.
+
foo

+````````````````````````````````
+
+
+```````````````````````````````` example
+____foo____
+.
+
foo

+````````````````````````````````
+
+
+
+Rule 13 can be applied to arbitrarily long sequences of
+delimiters:
+
+```````````````````````````````` example
+******foo******
+.
+
foo

+````````````````````````````````
+
+
+Rule 14:
+
+```````````````````````````````` example
+***foo***
+.
+
foo

+````````````````````````````````
+
+
+```````````````````````````````` example
+_____foo_____
+.
+
foo

+````````````````````````````````
+
+
+Rule 15:
+
+```````````````````````````````` example
+*foo _bar* baz_
+.
+
foo _bar baz_

+````````````````````````````````
+
+
+```````````````````````````````` example
+*foo __bar *baz bim__ bam*
+.
+
foo bar *baz bim bam

+````````````````````````````````
+
+
+Rule 16:
+
+```````````````````````````````` example
+**foo **bar baz**
+.
+
**foo bar baz

+````````````````````````````````
+
+
+```````````````````````````````` example
+*foo *bar baz*
+.
+
*foo bar baz

+````````````````````````````````
+
+
+Rule 17:
+
+```````````````````````````````` example
+*[bar*](/url)
+.
+
*bar*

+````````````````````````````````
+
+
+```````````````````````````````` example
+_foo [bar_](/url)
+.
+
_foo bar_

+````````````````````````````````
+
+
+```````````````````````````````` example
+*
+.
+
*

+````````````````````````````````
+
+
+```````````````````````````````` example
+**
+.
+
**

+````````````````````````````````
+
+
+```````````````````````````````` example
+__
+.
+
__

+````````````````````````````````
+
+
+```````````````````````````````` example
+*a `*`*
+.
+
a *

+````````````````````````````````
+
+
+```````````````````````````````` example
+_a `_`_
+.
+
a _

+````````````````````````````````
+
+
+```````````````````````````````` example
+**a
+.
+
**ahttp://foo.bar/?q=**

+````````````````````````````````
+
+
+```````````````````````````````` example
+__a
+.
+
__ahttp://foo.bar/?q=__

+````````````````````````````````
+
+
+
+## Links
+
+A link contains [link text] (the visible text), a [link destination]
+(the URI that is the link destination), and optionally a [link title].
+There are two basic kinds of links in Markdown.  In [inline links] the
+destination and title are given immediately after the link text.  In
+[reference links] the destination and title are defined elsewhere in
+the document.
+
+A [link text](@) consists of a sequence of zero or more
+inline elements enclosed by square brackets (`[` and `]`).  The
+following rules apply:
+
+- Links may not contain other links, at any level of nesting. If
+  multiple otherwise valid link definitions appear nested inside each
+  other, the inner-most definition is used.
+
+- Brackets are allowed in the [link text] only if (a) they
+  are backslash-escaped or (b) they appear as a matched pair of brackets,
+  with an open bracket `[`, a sequence of zero or more inlines, and
+  a close bracket `]`.
+
+- Backtick [code spans], [autolinks], and raw [HTML tags] bind more tightly
+  than the brackets in link text.  Thus, for example,
+  `` [foo`]` `` could not be a link text, since the second `]`
+  is part of a code span.
+
+- The brackets in link text bind more tightly than markers for
+  [emphasis and strong emphasis]. Thus, for example, `*[foo*](url)` is a link.
+
+A [link destination](@) consists of either
+
+- a sequence of zero or more characters between an opening `<` and a
+  closing `>` that contains no line endings or unescaped
+  `<` or `>` characters, or
+
+- a nonempty sequence of characters that does not start with `<`,
+  does not include [ASCII control characters][ASCII control character]
+  or [space] character, and includes parentheses only if (a) they are
+  backslash-escaped or (b) they are part of a balanced pair of
+  unescaped parentheses.
+  (Implementations may impose limits on parentheses nesting to
+  avoid performance issues, but at least three levels of nesting
+  should be supported.)
+
+A [link title](@)  consists of either
+
+- a sequence of zero or more characters between straight double-quote
+  characters (`"`), including a `"` character only if it is
+  backslash-escaped, or
+
+- a sequence of zero or more characters between straight single-quote
+  characters (`'`), including a `'` character only if it is
+  backslash-escaped, or
+
+- a sequence of zero or more characters between matching parentheses
+  (`(...)`), including a `(` or `)` character only if it is
+  backslash-escaped.
+
+Although [link titles] may span multiple lines, they may not contain
+a [blank line].
+
+An [inline link](@) consists of a [link text] followed immediately
+by a left parenthesis `(`, an optional [link destination], an optional
+[link title], and a right parenthesis `)`.
+These four components may be separated by spaces, tabs, and up to one line
+ending.
+If both [link destination] and [link title] are present, they *must* be
+separated by spaces, tabs, and up to one line ending.
+
+The link's text consists of the inlines contained
+in the [link text] (excluding the enclosing square brackets).
+The link's URI consists of the link destination, excluding enclosing
+`<...>` if present, with backslash-escapes in effect as described
+above.  The link's title consists of the link title, excluding its
+enclosing delimiters, with backslash-escapes in effect as described
+above.
+
+Here is a simple inline link:
+
+```````````````````````````````` example
+[link](/uri "title")
+.
+
link

+````````````````````````````````
+
+
+The title, the link text and even 
+the destination may be omitted:
+
+```````````````````````````````` example
+[link](/uri)
+.
+
link

+````````````````````````````````
+
+```````````````````````````````` example
+[](./target.md)
+.
+

+````````````````````````````````
+
+
+```````````````````````````````` example
+[link]()
+.
+
link

+````````````````````````````````
+
+
+```````````````````````````````` example
+[link](<>)
+.
+
link

+````````````````````````````````
+
+
+```````````````````````````````` example
+[]()
+.
+

+````````````````````````````````
+
+The destination can only contain spaces if it is
+enclosed in pointy brackets:
+
+```````````````````````````````` example
+[link](/my uri)
+.
+
[link](/my uri)

+````````````````````````````````
+
+```````````````````````````````` example
+[link]()
+.
+
link

+````````````````````````````````
+
+The destination cannot contain line endings,
+even if enclosed in pointy brackets:
+
+```````````````````````````````` example
+[link](foo
+bar)
+.
+
[link](foo
+bar)

+````````````````````````````````
+
+```````````````````````````````` example
+[link]()
+.
+
[link]()

+````````````````````````````````
+
+The destination can contain `)` if it is enclosed
+in pointy brackets:
+
+```````````````````````````````` example
+[a]()
+.
+
a

+````````````````````````````````
+
+Pointy brackets that enclose links must be unescaped:
+
+```````````````````````````````` example
+[link]()
+.
+
[link](<foo>)

+````````````````````````````````
+
+These are not links, because the opening pointy bracket
+is not matched properly:
+
+```````````````````````````````` example
+[a](
+[a](c)
+.
+
[a](<b)c
+[a](<b)c>
+[a](c)

+````````````````````````````````
+
+Parentheses inside the link destination may be escaped:
+
+```````````````````````````````` example
+[link](\(foo\))
+.
+
link

+````````````````````````````````
+
+Any number of parentheses are allowed without escaping, as long as they are
+balanced:
+
+```````````````````````````````` example
+[link](foo(and(bar)))
+.
+
link

+````````````````````````````````
+
+However, if you have unbalanced parentheses, you need to escape or use the
+`<...>` form:
+
+```````````````````````````````` example
+[link](foo(and(bar))
+.
+
[link](foo(and(bar))

+````````````````````````````````
+
+
+```````````````````````````````` example
+[link](foo\(and\(bar\))
+.
+
link

+````````````````````````````````
+
+
+```````````````````````````````` example
+[link]()
+.
+
link

+````````````````````````````````
+
+
+Parentheses and other symbols can also be escaped, as usual
+in Markdown:
+
+```````````````````````````````` example
+[link](foo\)\:)
+.
+
link

+````````````````````````````````
+
+
+A link can contain fragment identifiers and queries:
+
+```````````````````````````````` example
+[link](#fragment)
+
+[link](http://example.com#fragment)
+
+[link](http://example.com?foo=3#frag)
+.
+
link

+
link

+
link

+````````````````````````````````
+
+
+Note that a backslash before a non-escapable character is
+just a backslash:
+
+```````````````````````````````` example
+[link](foo\bar)
+.
+
link

+````````````````````````````````
+
+
+URL-escaping should be left alone inside the destination, as all
+URL-escaped characters are also valid URL characters. Entity and
+numerical character references in the destination will be parsed
+into the corresponding Unicode code points, as usual.  These may
+be optionally URL-escaped when written as HTML, but this spec
+does not enforce any particular policy for rendering URLs in
+HTML or other formats.  Renderers may make different decisions
+about how to escape or normalize URLs in the output.
+
+```````````````````````````````` example
+[link](foo%20bä)
+.
+
link

+````````````````````````````````
+
+
+Note that, because titles can often be parsed as destinations,
+if you try to omit the destination and keep the title, you'll
+get unexpected results:
+
+```````````````````````````````` example
+[link]("title")
+.
+
link

+````````````````````````````````
+
+
+Titles may be in single quotes, double quotes, or parentheses:
+
+```````````````````````````````` example
+[link](/url "title")
+[link](/url 'title')
+[link](/url (title))
+.
+
link
+link
+link

+````````````````````````````````
+
+
+Backslash escapes and entity and numeric character references
+may be used in titles:
+
+```````````````````````````````` example
+[link](/url "title \""")
+.
+
link

+````````````````````````````````
+
+
+Titles must be separated from the link using spaces, tabs, and up to one line
+ending.
+Other [Unicode whitespace] like non-breaking space doesn't work.
+
+```````````````````````````````` example
+[link](/url "title")
+.
+
link

+````````````````````````````````
+
+
+Nested balanced quotes are not allowed without escaping:
+
+```````````````````````````````` example
+[link](/url "title "and" title")
+.
+
[link](/url "title "and" title")

+````````````````````````````````
+
+
+But it is easy to work around this by using a different quote type:
+
+```````````````````````````````` example
+[link](/url 'title "and" title')
+.
+
link

+````````````````````````````````
+
+
+(Note:  `Markdown.pl` did allow double quotes inside a double-quoted
+title, and its test suite included a test demonstrating this.
+But it is hard to see a good rationale for the extra complexity this
+brings, since there are already many ways---backslash escaping,
+entity and numeric character references, or using a different
+quote type for the enclosing title---to write titles containing
+double quotes.  `Markdown.pl`'s handling of titles has a number
+of other strange features.  For example, it allows single-quoted
+titles in inline links, but not reference links.  And, in
+reference links but not inline links, it allows a title to begin
+with `"` and end with `)`.  `Markdown.pl` 1.0.1 even allows
+titles with no closing quotation mark, though 1.0.2b8 does not.
+It seems preferable to adopt a simple, rational rule that works
+the same way in inline links and link reference definitions.)
+
+Spaces, tabs, and up to one line ending is allowed around the destination and
+title:
+
+```````````````````````````````` example
+[link](   /uri
+  "title"  )
+.
+
link

+````````````````````````````````
+
+
+But it is not allowed between the link text and the
+following parenthesis:
+
+```````````````````````````````` example
+[link] (/uri)
+.
+
[link] (/uri)

+````````````````````````````````
+
+
+The link text may contain balanced brackets, but not unbalanced ones,
+unless they are escaped:
+
+```````````````````````````````` example
+[link [foo [bar]]](/uri)
+.
+
link [foo [bar]]

+````````````````````````````````
+
+
+```````````````````````````````` example
+[link] bar](/uri)
+.
+
[link] bar](/uri)

+````````````````````````````````
+
+
+```````````````````````````````` example
+[link [bar](/uri)
+.
+
[link bar

+````````````````````````````````
+
+
+```````````````````````````````` example
+[link \[bar](/uri)
+.
+
link [bar

+````````````````````````````````
+
+
+The link text may contain inline content:
+
+```````````````````````````````` example
+[link *foo **bar** `#`*](/uri)
+.
+
link foo bar #

+````````````````````````````````
+
+
+```````````````````````````````` example
+[![moon](moon.jpg)](/uri)
+.
+
moon

+````````````````````````````````
+
+
+However, links may not contain other links, at any level of nesting.
+
+```````````````````````````````` example
+[foo [bar](/uri)](/uri)
+.
+
[foo bar](/uri)

+````````````````````````````````
+
+
+```````````````````````````````` example
+[foo *[bar [baz](/uri)](/uri)*](/uri)
+.
+
[foo [bar baz](/uri)](/uri)

+````````````````````````````````
+
+
+```````````````````````````````` example
+![[[foo](uri1)](uri2)](uri3)
+.
+
[foo](uri2)

+````````````````````````````````
+
+
+These cases illustrate the precedence of link text grouping over
+emphasis grouping:
+
+```````````````````````````````` example
+*[foo*](/uri)
+.
+
*foo*

+````````````````````````````````
+
+
+```````````````````````````````` example
+[foo *bar](baz*)
+.
+
foo *bar

+````````````````````````````````
+
+
+Note that brackets that *aren't* part of links do not take
+precedence:
+
+```````````````````````````````` example
+*foo [bar* baz]
+.
+
foo [bar baz]

+````````````````````````````````
+
+
+These cases illustrate the precedence of HTML tags, code spans,
+and autolinks over link grouping:
+
+```````````````````````````````` example
+[foo 
+.
+
[foo 

+````````````````````````````````
+
+
+```````````````````````````````` example
+[foo`](/uri)`
+.
+
[foo](/uri)

+````````````````````````````````
+
+
+```````````````````````````````` example
+[foo
+.
+
[foohttp://example.com/?search=](uri)

+````````````````````````````````
+
+
+There are three kinds of [reference link](@)s:
+[full](#full-reference-link), [collapsed](#collapsed-reference-link),
+and [shortcut](#shortcut-reference-link).
+
+A [full reference link](@)
+consists of a [link text] immediately followed by a [link label]
+that [matches] a [link reference definition] elsewhere in the document.
+
+A [link label](@)  begins with a left bracket (`[`) and ends
+with the first right bracket (`]`) that is not backslash-escaped.
+Between these brackets there must be at least one character that is not a space,
+tab, or line ending.
+Unescaped square bracket characters are not allowed inside the
+opening and closing square brackets of [link labels].  A link
+label can have at most 999 characters inside the square
+brackets.
+
+One label [matches](@)
+another just in case their normalized forms are equal.  To normalize a
+label, strip off the opening and closing brackets,
+perform the *Unicode case fold*, strip leading and trailing
+spaces, tabs, and line endings, and collapse consecutive internal
+spaces, tabs, and line endings to a single space.  If there are multiple
+matching reference link definitions, the one that comes first in the
+document is used.  (It is desirable in such cases to emit a warning.)
+
+The link's URI and title are provided by the matching [link
+reference definition].
+
+Here is a simple example:
+
+```````````````````````````````` example
+[foo][bar]
+
+[bar]: /url "title"
+.
+
foo

+````````````````````````````````
+
+
+The rules for the [link text] are the same as with
+[inline links].  Thus:
+
+The link text may contain balanced brackets, but not unbalanced ones,
+unless they are escaped:
+
+```````````````````````````````` example
+[link [foo [bar]]][ref]
+
+[ref]: /uri
+.
+
link [foo [bar]]

+````````````````````````````````
+
+
+```````````````````````````````` example
+[link \[bar][ref]
+
+[ref]: /uri
+.
+
link [bar

+````````````````````````````````
+
+
+The link text may contain inline content:
+
+```````````````````````````````` example
+[link *foo **bar** `#`*][ref]
+
+[ref]: /uri
+.
+
link foo bar #

+````````````````````````````````
+
+
+```````````````````````````````` example
+[![moon](moon.jpg)][ref]
+
+[ref]: /uri
+.
+
moon

+````````````````````````````````
+
+
+However, links may not contain other links, at any level of nesting.
+
+```````````````````````````````` example
+[foo [bar](/uri)][ref]
+
+[ref]: /uri
+.
+
[foo bar]ref

+````````````````````````````````
+
+
+```````````````````````````````` example
+[foo *bar [baz][ref]*][ref]
+
+[ref]: /uri
+.
+
[foo bar baz]ref

+````````````````````````````````
+
+
+(In the examples above, we have two [shortcut reference links]
+instead of one [full reference link].)
+
+The following cases illustrate the precedence of link text grouping over
+emphasis grouping:
+
+```````````````````````````````` example
+*[foo*][ref]
+
+[ref]: /uri
+.
+
*foo*

+````````````````````````````````
+
+
+```````````````````````````````` example
+[foo *bar][ref]*
+
+[ref]: /uri
+.
+
foo *bar*

+````````````````````````````````
+
+
+These cases illustrate the precedence of HTML tags, code spans,
+and autolinks over link grouping:
+
+```````````````````````````````` example
+[foo 
+
+[ref]: /uri
+.
+
[foo 

+````````````````````````````````
+
+
+```````````````````````````````` example
+[foo`][ref]`
+
+[ref]: /uri
+.
+
[foo][ref]

+````````````````````````````````
+
+
+```````````````````````````````` example
+[foo
+
+[ref]: /uri
+.
+
[foohttp://example.com/?search=][ref]

+````````````````````````````````
+
+
+Matching is case-insensitive:
+
+```````````````````````````````` example
+[foo][BaR]
+
+[bar]: /url "title"
+.
+
foo

+````````````````````````````````
+
+
+Unicode case fold is used:
+
+```````````````````````````````` example
+[ẞ]
+
+[SS]: /url
+.
+
ẞ

+````````````````````````````````
+
+
+Consecutive internal spaces, tabs, and line endings are treated as one space for
+purposes of determining matching:
+
+```````````````````````````````` example
+[Foo
+  bar]: /url
+
+[Baz][Foo bar]
+.
+
Baz

+````````````````````````````````
+
+
+No spaces, tabs, or line endings are allowed between the [link text] and the
+[link label]:
+
+```````````````````````````````` example
+[foo] [bar]
+
+[bar]: /url "title"
+.
+
[foo] bar

+````````````````````````````````
+
+
+```````````````````````````````` example
+[foo]
+[bar]
+
+[bar]: /url "title"
+.
+
[foo]
+bar

+````````````````````````````````
+
+
+This is a departure from John Gruber's original Markdown syntax
+description, which explicitly allows whitespace between the link
+text and the link label.  It brings reference links in line with
+[inline links], which (according to both original Markdown and
+this spec) cannot have whitespace after the link text.  More
+importantly, it prevents inadvertent capture of consecutive
+[shortcut reference links]. If whitespace is allowed between the
+link text and the link label, then in the following we will have
+a single reference link, not two shortcut reference links, as
+intended:
+
+``` markdown
+[foo]
+[bar]
+
+[foo]: /url1
+[bar]: /url2
+```
+
+(Note that [shortcut reference links] were introduced by Gruber
+himself in a beta version of `Markdown.pl`, but never included
+in the official syntax description.  Without shortcut reference
+links, it is harmless to allow space between the link text and
+link label; but once shortcut references are introduced, it is
+too dangerous to allow this, as it frequently leads to
+unintended results.)
+
+When there are multiple matching [link reference definitions],
+the first is used:
+
+```````````````````````````````` example
+[foo]: /url1
+
+[foo]: /url2
+
+[bar][foo]
+.
+
bar

+````````````````````````````````
+
+
+Note that matching is performed on normalized strings, not parsed
+inline content.  So the following does not match, even though the
+labels define equivalent inline content:
+
+```````````````````````````````` example
+[bar][foo\!]
+
+[foo!]: /url
+.
+
[bar][foo!]

+````````````````````````````````
+
+
+[Link labels] cannot contain brackets, unless they are
+backslash-escaped:
+
+```````````````````````````````` example
+[foo][ref[]
+
+[ref[]: /uri
+.
+
[foo][ref[]

+
[ref[]: /uri

+````````````````````````````````
+
+
+```````````````````````````````` example
+[foo][ref[bar]]
+
+[ref[bar]]: /uri
+.
+
[foo][ref[bar]]

+
[ref[bar]]: /uri

+````````````````````````````````
+
+
+```````````````````````````````` example
+[[[foo]]]
+
+[[[foo]]]: /url
+.
+
[[[foo]]]

+
[[[foo]]]: /url

+````````````````````````````````
+
+
+```````````````````````````````` example
+[foo][ref\[]
+
+[ref\[]: /uri
+.
+
foo

+````````````````````````````````
+
+
+Note that in this example `]` is not backslash-escaped:
+
+```````````````````````````````` example
+[bar\\]: /uri
+
+[bar\\]
+.
+
bar\

+````````````````````````````````
+
+
+A [link label] must contain at least one character that is not a space, tab, or
+line ending:
+
+```````````````````````````````` example
+[]
+
+[]: /uri
+.
+
[]

+
[]: /uri

+````````````````````````````````
+
+
+```````````````````````````````` example
+[
+ ]
+
+[
+ ]: /uri
+.
+
[
+]

+
[
+]: /uri

+````````````````````````````````
+
+
+A [collapsed reference link](@)
+consists of a [link label] that [matches] a
+[link reference definition] elsewhere in the
+document, followed by the string `[]`.
+The contents of the first link label are parsed as inlines,
+which are used as the link's text.  The link's URI and title are
+provided by the matching reference link definition.  Thus,
+`[foo][]` is equivalent to `[foo][foo]`.
+
+```````````````````````````````` example
+[foo][]
+
+[foo]: /url "title"
+.
+
foo

+````````````````````````````````
+
+
+```````````````````````````````` example
+[*foo* bar][]
+
+[*foo* bar]: /url "title"
+.
+
foo bar

+````````````````````````````````
+
+
+The link labels are case-insensitive:
+
+```````````````````````````````` example
+[Foo][]
+
+[foo]: /url "title"
+.
+
Foo

+````````````````````````````````
+
+
+
+As with full reference links, spaces, tabs, or line endings are not
+allowed between the two sets of brackets:
+
+```````````````````````````````` example
+[foo] 
+[]
+
+[foo]: /url "title"
+.
+
foo
+[]

+````````````````````````````````
+
+
+A [shortcut reference link](@)
+consists of a [link label] that [matches] a
+[link reference definition] elsewhere in the
+document and is not followed by `[]` or a link label.
+The contents of the first link label are parsed as inlines,
+which are used as the link's text.  The link's URI and title
+are provided by the matching link reference definition.
+Thus, `[foo]` is equivalent to `[foo][]`.
+
+```````````````````````````````` example
+[foo]
+
+[foo]: /url "title"
+.
+
foo

+````````````````````````````````
+
+
+```````````````````````````````` example
+[*foo* bar]
+
+[*foo* bar]: /url "title"
+.
+
foo bar

+````````````````````````````````
+
+
+```````````````````````````````` example
+[[*foo* bar]]
+
+[*foo* bar]: /url "title"
+.
+
[foo bar]

+````````````````````````````````
+
+
+```````````````````````````````` example
+[[bar [foo]
+
+[foo]: /url
+.
+
[[bar foo

+````````````````````````````````
+
+
+The link labels are case-insensitive:
+
+```````````````````````````````` example
+[Foo]
+
+[foo]: /url "title"
+.
+
Foo

+````````````````````````````````
+
+
+A space after the link text should be preserved:
+
+```````````````````````````````` example
+[foo] bar
+
+[foo]: /url
+.
+
foo bar

+````````````````````````````````
+
+
+If you just want bracketed text, you can backslash-escape the
+opening bracket to avoid links:
+
+```````````````````````````````` example
+\[foo]
+
+[foo]: /url "title"
+.
+
[foo]

+````````````````````````````````
+
+
+Note that this is a link, because a link label ends with the first
+following closing bracket:
+
+```````````````````````````````` example
+[foo*]: /url
+
+*[foo*]
+.
+
*foo*

+````````````````````````````````
+
+
+Full and compact references take precedence over shortcut
+references:
+
+```````````````````````````````` example
+[foo][bar]
+
+[foo]: /url1
+[bar]: /url2
+.
+
foo

+````````````````````````````````
+
+```````````````````````````````` example
+[foo][]
+
+[foo]: /url1
+.
+
foo

+````````````````````````````````
+
+Inline links also take precedence:
+
+```````````````````````````````` example
+[foo]()
+
+[foo]: /url1
+.
+
foo

+````````````````````````````````
+
+```````````````````````````````` example
+[foo](not a link)
+
+[foo]: /url1
+.
+
foo(not a link)

+````````````````````````````````
+
+In the following case `[bar][baz]` is parsed as a reference,
+`[foo]` as normal text:
+
+```````````````````````````````` example
+[foo][bar][baz]
+
+[baz]: /url
+.
+
[foo]bar

+````````````````````````````````
+
+
+Here, though, `[foo][bar]` is parsed as a reference, since
+`[bar]` is defined:
+
+```````````````````````````````` example
+[foo][bar][baz]
+
+[baz]: /url1
+[bar]: /url2
+.
+
foobaz

+````````````````````````````````
+
+
+Here `[foo]` is not parsed as a shortcut reference, because it
+is followed by a link label (even though `[bar]` is not defined):
+
+```````````````````````````````` example
+[foo][bar][baz]
+
+[baz]: /url1
+[foo]: /url2
+.
+
[foo]bar

+````````````````````````````````
+
+
+
+## Images
+
+Syntax for images is like the syntax for links, with one
+difference. Instead of [link text], we have an
+[image description](@).  The rules for this are the
+same as for [link text], except that (a) an
+image description starts with `![` rather than `[`, and
+(b) an image description may contain links.
+An image description has inline elements
+as its contents.  When an image is rendered to HTML,
+this is standardly used as the image's `alt` attribute.
+
+```````````````````````````````` example
+![foo](/url "title")
+.
+
foo

+````````````````````````````````
+
+
+```````````````````````````````` example
+![foo *bar*]
+
+[foo *bar*]: train.jpg "train & tracks"
+.
+
foo bar

+````````````````````````````````
+
+
+```````````````````````````````` example
+![foo ![bar](/url)](/url2)
+.
+
foo bar

+````````````````````````````````
+
+
+```````````````````````````````` example
+![foo [bar](/url)](/url2)
+.
+
foo bar

+````````````````````````````````
+
+
+Though this spec is concerned with parsing, not rendering, it is
+recommended that in rendering to HTML, only the plain string content
+of the [image description] be used.  Note that in
+the above example, the alt attribute's value is `foo bar`, not `foo
+[bar](/url)` or `foo bar`.  Only the plain string
+content is rendered, without formatting.
+
+```````````````````````````````` example
+![foo *bar*][]
+
+[foo *bar*]: train.jpg "train & tracks"
+.
+
foo bar

+````````````````````````````````
+
+
+```````````````````````````````` example
+![foo *bar*][foobar]
+
+[FOOBAR]: train.jpg "train & tracks"
+.
+
foo bar

+````````````````````````````````
+
+
+```````````````````````````````` example
+![foo](train.jpg)
+.
+
foo

+````````````````````````````````
+
+
+```````````````````````````````` example
+My ![foo bar](/path/to/train.jpg  "title"   )
+.
+
My foo bar

+````````````````````````````````
+
+
+```````````````````````````````` example
+![foo]()
+.
+
foo

+````````````````````````````````
+
+
+```````````````````````````````` example
+![](/url)
+.
+

+````````````````````````````````
+
+
+Reference-style:
+
+```````````````````````````````` example
+![foo][bar]
+
+[bar]: /url
+.
+
foo

+````````````````````````````````
+
+
+```````````````````````````````` example
+![foo][bar]
+
+[BAR]: /url
+.
+
foo

+````````````````````````````````
+
+
+Collapsed:
+
+```````````````````````````````` example
+![foo][]
+
+[foo]: /url "title"
+.
+
foo

+````````````````````````````````
+
+
+```````````````````````````````` example
+![*foo* bar][]
+
+[*foo* bar]: /url "title"
+.
+
foo bar

+````````````````````````````````
+
+
+The labels are case-insensitive:
+
+```````````````````````````````` example
+![Foo][]
+
+[foo]: /url "title"
+.
+
Foo

+````````````````````````````````
+
+
+As with reference links, spaces, tabs, and line endings, are not allowed
+between the two sets of brackets:
+
+```````````````````````````````` example
+![foo] 
+[]
+
+[foo]: /url "title"
+.
+
foo
+[]

+````````````````````````````````
+
+
+Shortcut:
+
+```````````````````````````````` example
+![foo]
+
+[foo]: /url "title"
+.
+
foo

+````````````````````````````````
+
+
+```````````````````````````````` example
+![*foo* bar]
+
+[*foo* bar]: /url "title"
+.
+
foo bar

+````````````````````````````````
+
+
+Note that link labels cannot contain unescaped brackets:
+
+```````````````````````````````` example
+![[foo]]
+
+[[foo]]: /url "title"
+.
+
![[foo]]

+
[[foo]]: /url "title"

+````````````````````````````````
+
+
+The link labels are case-insensitive:
+
+```````````````````````````````` example
+![Foo]
+
+[foo]: /url "title"
+.
+
Foo

+````````````````````````````````
+
+
+If you just want a literal `!` followed by bracketed text, you can
+backslash-escape the opening `[`:
+
+```````````````````````````````` example
+!\[foo]
+
+[foo]: /url "title"
+.
+
![foo]

+````````````````````````````````
+
+
+If you want a link after a literal `!`, backslash-escape the
+`!`:
+
+```````````````````````````````` example
+\![foo]
+
+[foo]: /url "title"
+.
+
!foo

+````````````````````````````````
+
+
+## Autolinks
+
+[Autolink](@)s are absolute URIs and email addresses inside
+`<` and `>`. They are parsed as links, with the URL or email address
+as the link label.
+
+A [URI autolink](@) consists of `<`, followed by an
+[absolute URI] followed by `>`.  It is parsed as
+a link to the URI, with the URI as the link's label.
+
+An [absolute URI](@),
+for these purposes, consists of a [scheme] followed by a colon (`:`)
+followed by zero or more characters other [ASCII control
+characters][ASCII control character], [space], `<`, and `>`.
+If the URI includes these characters, they must be percent-encoded
+(e.g. `%20` for a space).
+
+For purposes of this spec, a [scheme](@) is any sequence
+of 2--32 characters beginning with an ASCII letter and followed
+by any combination of ASCII letters, digits, or the symbols plus
+("+"), period ("."), or hyphen ("-").
+
+Here are some valid autolinks:
+
+```````````````````````````````` example
+
+.
+
http://foo.bar.baz

+````````````````````````````````
+
+
+```````````````````````````````` example
+
+.
+
http://foo.bar.baz/test?q=hello&id=22&boolean

+````````````````````````````````
+
+
+```````````````````````````````` example
+
+.
+
irc://foo.bar:2233/baz

+````````````````````````````````
+
+
+Uppercase is also fine:
+
+```````````````````````````````` example
+
+.
+
MAILTO:FOO@BAR.BAZ

+````````````````````````````````
+
+
+Note that many strings that count as [absolute URIs] for
+purposes of this spec are not valid URIs, because their
+schemes are not registered or because of other problems
+with their syntax:
+
+```````````````````````````````` example
+
+.
+
a+b+c:d

+````````````````````````````````
+
+
+```````````````````````````````` example
+
+.
+
made-up-scheme://foo,bar

+````````````````````````````````
+
+
+```````````````````````````````` example
+
+.
+
http://../

+````````````````````````````````
+
+
+```````````````````````````````` example
+
+.
+
localhost:5001/foo

+````````````````````````````````
+
+
+Spaces are not allowed in autolinks:
+
+```````````````````````````````` example
+
+.
+
<http://foo.bar/baz bim>

+````````````````````````````````
+
+
+Backslash-escapes do not work inside autolinks:
+
+```````````````````````````````` example
+
+.
+
http://example.com/\[\

+````````````````````````````````
+
+
+An [email autolink](@)
+consists of `<`, followed by an [email address],
+followed by `>`.  The link's label is the email address,
+and the URL is `mailto:` followed by the email address.
+
+An [email address](@),
+for these purposes, is anything that matches
+the [non-normative regex from the HTML5
+spec](https://html.spec.whatwg.org/multipage/forms.html#e-mail-state-(type=email)):
+
+    /^[a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?
+    (?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$/
+
+Examples of email autolinks:
+
+```````````````````````````````` example
+
+.
+
foo@bar.example.com

+````````````````````````````````
+
+
+```````````````````````````````` example
+
+.
+
foo+special@Bar.baz-bar0.com

+````````````````````````````````
+
+
+Backslash-escapes do not work inside email autolinks:
+
+```````````````````````````````` example
+
+.
+
<foo+@bar.example.com>

+````````````````````````````````
+
+
+These are not autolinks:
+
+```````````````````````````````` example
+<>
+.
+
<>

+````````````````````````````````
+
+
+```````````````````````````````` example
+< http://foo.bar >
+.
+
< http://foo.bar >

+````````````````````````````````
+
+
+```````````````````````````````` example
+
+.
+
<m:abc>

+````````````````````````````````
+
+
+```````````````````````````````` example
+
+.
+
<foo.bar.baz>

+````````````````````````````````
+
+
+```````````````````````````````` example
+http://example.com
+.
+
http://example.com

+````````````````````````````````
+
+
+```````````````````````````````` example
+foo@bar.example.com
+.
+
foo@bar.example.com

+````````````````````````````````
+
+
+## Raw HTML
+
+Text between `<` and `>` that looks like an HTML tag is parsed as a
+raw HTML tag and will be rendered in HTML without escaping.
+Tag and attribute names are not limited to current HTML tags,
+so custom tags (and even, say, DocBook tags) may be used.
+
+Here is the grammar for tags:
+
+A [tag name](@) consists of an ASCII letter
+followed by zero or more ASCII letters, digits, or
+hyphens (`-`).
+
+An [attribute](@) consists of spaces, tabs, and up to one line ending,
+an [attribute name], and an optional
+[attribute value specification].
+
+An [attribute name](@)
+consists of an ASCII letter, `_`, or `:`, followed by zero or more ASCII
+letters, digits, `_`, `.`, `:`, or `-`.  (Note:  This is the XML
+specification restricted to ASCII.  HTML5 is laxer.)
+
+An [attribute value specification](@)
+consists of optional spaces, tabs, and up to one line ending,
+a `=` character, optional spaces, tabs, and up to one line ending,
+and an [attribute value].
+
+An [attribute value](@)
+consists of an [unquoted attribute value],
+a [single-quoted attribute value], or a [double-quoted attribute value].
+
+An [unquoted attribute value](@)
+is a nonempty string of characters not
+including spaces, tabs, line endings, `"`, `'`, `=`, `<`, `>`, or `` ` ``.
+
+A [single-quoted attribute value](@)
+consists of `'`, zero or more
+characters not including `'`, and a final `'`.
+
+A [double-quoted attribute value](@)
+consists of `"`, zero or more
+characters not including `"`, and a final `"`.
+
+An [open tag](@) consists of a `<` character, a [tag name],
+zero or more [attributes], optional spaces, tabs, and up to one line ending,
+an optional `/` character, and a `>` character.
+
+A [closing tag](@) consists of the string ``.
+
+An [HTML comment](@) consists of ``,
+where *text* does not start with `>` or `->`, does not end with `-`,
+and does not contain `--`.  (See the
+[HTML5 spec](http://www.w3.org/TR/html5/syntax.html#comments).)
+
+A [processing instruction](@)
+consists of the string ``, and the string
+`?>`.
+
+A [declaration](@) consists of the string ``, and the character `>`.
+
+A [CDATA section](@) consists of
+the string ``, and the string `]]>`.
+
+An [HTML tag](@) consists of an [open tag], a [closing tag],
+an [HTML comment], a [processing instruction], a [declaration],
+or a [CDATA section].
+
+Here are some simple open tags:
+
+```````````````````````````````` example
+
+.
+

+````````````````````````````````
+
+
+Empty elements:
+
+```````````````````````````````` example
+
+.
+

+````````````````````````````````
+
+
+Whitespace is allowed:
+
+```````````````````````````````` example
+
+.
+

+````````````````````````````````
+
+
+With attributes:
+
+```````````````````````````````` example
+
+.
+

+````````````````````````````````
+
+
+Custom tag names can be used:
+
+```````````````````````````````` example
+Foo 
+.
+
Foo 

+````````````````````````````````
+
+
+Illegal tag names, not parsed as HTML:
+
+```````````````````````````````` example
+<33> <__>
+.
+
<33> <__>

+````````````````````````````````
+
+
+Illegal attribute names:
+
+```````````````````````````````` example
+
+.
+
<a h*#ref="hi">

+````````````````````````````````
+
+
+Illegal attribute values:
+
+```````````````````````````````` example
+
+.
+
</a href="foo">

+````````````````````````````````
+
+
+Comments:
+
+```````````````````````````````` example
+foo 
+.
+
foo 

+````````````````````````````````
+
+
+```````````````````````````````` example
+foo 
+.
+
foo <!-- not a comment -- two hyphens -->

+````````````````````````````````
+
+
+Not comments:
+
+```````````````````````````````` example
+foo  foo -->
+
+foo 
+.
+
foo <!--> foo -->

+
foo <!-- foo--->

+````````````````````````````````
+
+
+Processing instructions:
+
+```````````````````````````````` example
+foo 
+.
+
foo 

+````````````````````````````````
+
+
+Declarations:
+
+```````````````````````````````` example
+foo 
+.
+
foo 

+````````````````````````````````
+
+
+CDATA sections:
+
+```````````````````````````````` example
+foo &<]]>
+.
+
foo &<]]>

+````````````````````````````````
+
+
+Entity and numeric character references are preserved in HTML
+attributes:
+
+```````````````````````````````` example
+foo 
+.
+
foo 

+````````````````````````````````
+
+
+Backslash escapes do not work in HTML attributes:
+
+```````````````````````````````` example
+foo 
+.
+
foo 

+````````````````````````````````
+
+
+```````````````````````````````` example
+
+.
+
<a href=""">

+````````````````````````````````
+
+
+## Hard line breaks
+
+A line ending (not in a code span or HTML tag) that is preceded
+by two or more spaces and does not occur at the end of a block
+is parsed as a [hard line break](@) (rendered
+in HTML as a `
` tag):
+
+```````````````````````````````` example
+foo  
+baz
+.
+
foo

+baz

+````````````````````````````````
+
+
+For a more visible alternative, a backslash before the
+[line ending] may be used instead of two or more spaces:
+
+```````````````````````````````` example
+foo\
+baz
+.
+
foo

+baz

+````````````````````````````````
+
+
+More than two spaces can be used:
+
+```````````````````````````````` example
+foo       
+baz
+.
+
foo

+baz

+````````````````````````````````
+
+
+Leading spaces at the beginning of the next line are ignored:
+
+```````````````````````````````` example
+foo  
+     bar
+.
+
foo

+bar

+````````````````````````````````
+
+
+```````````````````````````````` example
+foo\
+     bar
+.
+
foo

+bar

+````````````````````````````````
+
+
+Hard line breaks can occur inside emphasis, links, and other constructs
+that allow inline content:
+
+```````````````````````````````` example
+*foo  
+bar*
+.
+
foo

+bar

+````````````````````````````````
+
+
+```````````````````````````````` example
+*foo\
+bar*
+.
+
foo

+bar

+````````````````````````````````
+
+
+Hard line breaks do not occur inside code spans
+
+```````````````````````````````` example
+`code  
+span`
+.
+
code   span

+````````````````````````````````
+
+
+```````````````````````````````` example
+`code\
+span`
+.
+
code\ span

+````````````````````````````````
+
+
+or HTML tags:
+
+```````````````````````````````` example
+
+.
+

+````````````````````````````````
+
+
+```````````````````````````````` example
+
+.
+

+````````````````````````````````
+
+
+Hard line breaks are for separating inline content within a block.
+Neither syntax for hard line breaks works at the end of a paragraph or
+other block element:
+
+```````````````````````````````` example
+foo\
+.
+
foo\

+````````````````````````````````
+
+
+```````````````````````````````` example
+foo  
+.
+
foo

+````````````````````````````````
+
+
+```````````````````````````````` example
+### foo\
+.
+
foo\

+````````````````````````````````
+
+
+```````````````````````````````` example
+### foo  
+.
+
foo

+````````````````````````````````
+
+
+## Soft line breaks
+
+A regular line ending (not in a code span or HTML tag) that is not
+preceded by two or more spaces or a backslash is parsed as a
+[softbreak](@).  (A soft line break may be rendered in HTML either as a
+[line ending] or as a space. The result will be the same in
+browsers. In the examples here, a [line ending] will be used.)
+
+```````````````````````````````` example
+foo
+baz
+.
+
foo
+baz

+````````````````````````````````
+
+
+Spaces at the end of the line and beginning of the next line are
+removed:
+
+```````````````````````````````` example
+foo 
+ baz
+.
+
foo
+baz

+````````````````````````````````
+
+
+A conforming parser may render a soft line break in HTML either as a
+line ending or as a space.
+
+A renderer may also provide an option to render soft line breaks
+as hard line breaks.
+
+## Textual content
+
+Any characters not given an interpretation by the above rules will
+be parsed as plain textual content.
+
+```````````````````````````````` example
+hello $.;'there
+.
+
hello $.;'there

+````````````````````````````````
+
+
+```````````````````````````````` example
+Foo χρῆν
+.
+
Foo χρῆν

+````````````````````````````````
+
+
+Internal spaces are preserved verbatim:
+
+```````````````````````````````` example
+Multiple     spaces
+.
+
Multiple     spaces

+````````````````````````````````
+
+
+
+
+# Appendix: A parsing strategy
+
+In this appendix we describe some features of the parsing strategy
+used in the CommonMark reference implementations.
+
+## Overview
+
+Parsing has two phases:
+
+1. In the first phase, lines of input are consumed and the block
+structure of the document---its division into paragraphs, block quotes,
+list items, and so on---is constructed.  Text is assigned to these
+blocks but not parsed. Link reference definitions are parsed and a
+map of links is constructed.
+
+2. In the second phase, the raw text contents of paragraphs and headings
+are parsed into sequences of Markdown inline elements (strings,
+code spans, links, emphasis, and so on), using the map of link
+references constructed in phase 1.
+
+At each point in processing, the document is represented as a tree of
+**blocks**.  The root of the tree is a `document` block.  The `document`
+may have any number of other blocks as **children**.  These children
+may, in turn, have other blocks as children.  The last child of a block
+is normally considered **open**, meaning that subsequent lines of input
+can alter its contents.  (Blocks that are not open are **closed**.)
+Here, for example, is a possible document tree, with the open blocks
+marked by arrows:
+
+``` tree
+-> document
+  -> block_quote
+       paragraph
+         "Lorem ipsum dolor\nsit amet."
+    -> list (type=bullet tight=true bullet_char=-)
+         list_item
+           paragraph
+             "Qui *quodsi iracundia*"
+      -> list_item
+        -> paragraph
+             "aliquando id"
+```
+
+## Phase 1: block structure
+
+Each line that is processed has an effect on this tree.  The line is
+analyzed and, depending on its contents, the document may be altered
+in one or more of the following ways:
+
+1. One or more open blocks may be closed.
+2. One or more new blocks may be created as children of the
+   last open block.
+3. Text may be added to the last (deepest) open block remaining
+   on the tree.
+
+Once a line has been incorporated into the tree in this way,
+it can be discarded, so input can be read in a stream.
+
+For each line, we follow this procedure:
+
+1. First we iterate through the open blocks, starting with the
+root document, and descending through last children down to the last
+open block.  Each block imposes a condition that the line must satisfy
+if the block is to remain open.  For example, a block quote requires a
+`>` character.  A paragraph requires a non-blank line.
+In this phase we may match all or just some of the open
+blocks.  But we cannot close unmatched blocks yet, because we may have a
+[lazy continuation line].
+
+2.  Next, after consuming the continuation markers for existing
+blocks, we look for new block starts (e.g. `>` for a block quote).
+If we encounter a new block start, we close any blocks unmatched
+in step 1 before creating the new block as a child of the last
+matched container block.
+
+3.  Finally, we look at the remainder of the line (after block
+markers like `>`, list markers, and indentation have been consumed).
+This is text that can be incorporated into the last open
+block (a paragraph, code block, heading, or raw HTML).
+
+Setext headings are formed when we see a line of a paragraph
+that is a [setext heading underline].
+
+Reference link definitions are detected when a paragraph is closed;
+the accumulated text lines are parsed to see if they begin with
+one or more reference link definitions.  Any remainder becomes a
+normal paragraph.
+
+We can see how this works by considering how the tree above is
+generated by four lines of Markdown:
+
+``` markdown
+> Lorem ipsum dolor
+sit amet.
+> - Qui *quodsi iracundia*
+> - aliquando id
+```
+
+At the outset, our document model is just
+
+``` tree
+-> document
+```
+
+The first line of our text,
+
+``` markdown
+> Lorem ipsum dolor
+```
+
+causes a `block_quote` block to be created as a child of our
+open `document` block, and a `paragraph` block as a child of
+the `block_quote`.  Then the text is added to the last open
+block, the `paragraph`:
+
+``` tree
+-> document
+  -> block_quote
+    -> paragraph
+         "Lorem ipsum dolor"
+```
+
+The next line,
+
+``` markdown
+sit amet.
+```
+
+is a "lazy continuation" of the open `paragraph`, so it gets added
+to the paragraph's text:
+
+``` tree
+-> document
+  -> block_quote
+    -> paragraph
+         "Lorem ipsum dolor\nsit amet."
+```
+
+The third line,
+
+``` markdown
+> - Qui *quodsi iracundia*
+```
+
+causes the `paragraph` block to be closed, and a new `list` block
+opened as a child of the `block_quote`.  A `list_item` is also
+added as a child of the `list`, and a `paragraph` as a child of
+the `list_item`.  The text is then added to the new `paragraph`:
+
+``` tree
+-> document
+  -> block_quote
+       paragraph
+         "Lorem ipsum dolor\nsit amet."
+    -> list (type=bullet tight=true bullet_char=-)
+      -> list_item
+        -> paragraph
+             "Qui *quodsi iracundia*"
+```
+
+The fourth line,
+
+``` markdown
+> - aliquando id
+```
+
+causes the `list_item` (and its child the `paragraph`) to be closed,
+and a new `list_item` opened up as child of the `list`.  A `paragraph`
+is added as a child of the new `list_item`, to contain the text.
+We thus obtain the final tree:
+
+``` tree
+-> document
+  -> block_quote
+       paragraph
+         "Lorem ipsum dolor\nsit amet."
+    -> list (type=bullet tight=true bullet_char=-)
+         list_item
+           paragraph
+             "Qui *quodsi iracundia*"
+      -> list_item
+        -> paragraph
+             "aliquando id"
+```
+
+## Phase 2: inline structure
+
+Once all of the input has been parsed, all open blocks are closed.
+
+We then "walk the tree," visiting every node, and parse raw
+string contents of paragraphs and headings as inlines.  At this
+point we have seen all the link reference definitions, so we can
+resolve reference links as we go.
+
+``` tree
+document
+  block_quote
+    paragraph
+      str "Lorem ipsum dolor"
+      softbreak
+      str "sit amet."
+    list (type=bullet tight=true bullet_char=-)
+      list_item
+        paragraph
+          str "Qui "
+          emph
+            str "quodsi iracundia"
+      list_item
+        paragraph
+          str "aliquando id"
+```
+
+Notice how the [line ending] in the first paragraph has
+been parsed as a `softbreak`, and the asterisks in the first list item
+have become an `emph`.
+
+### An algorithm for parsing nested emphasis and links
+
+By far the trickiest part of inline parsing is handling emphasis,
+strong emphasis, links, and images.  This is done using the following
+algorithm.
+
+When we're parsing inlines and we hit either
+
+- a run of `*` or `_` characters, or
+- a `[` or `![`
+
+we insert a text node with these symbols as its literal content, and we
+add a pointer to this text node to the [delimiter stack](@).
+
+The [delimiter stack] is a doubly linked list.  Each
+element contains a pointer to a text node, plus information about
+
+- the type of delimiter (`[`, `![`, `*`, `_`)
+- the number of delimiters,
+- whether the delimiter is "active" (all are active to start), and
+- whether the delimiter is a potential opener, a potential closer,
+  or both (which depends on what sort of characters precede
+  and follow the delimiters).
+
+When we hit a `]` character, we call the *look for link or image*
+procedure (see below).
+
+When we hit the end of the input, we call the *process emphasis*
+procedure (see below), with `stack_bottom` = NULL.
+
+#### *look for link or image*
+
+Starting at the top of the delimiter stack, we look backwards
+through the stack for an opening `[` or `![` delimiter.
+
+- If we don't find one, we return a literal text node `]`.
+
+- If we do find one, but it's not *active*, we remove the inactive
+  delimiter from the stack, and return a literal text node `]`.
+
+- If we find one and it's active, then we parse ahead to see if
+  we have an inline link/image, reference link/image, compact reference
+  link/image, or shortcut reference link/image.
+
+  + If we don't, then we remove the opening delimiter from the
+    delimiter stack and return a literal text node `]`.
+
+  + If we do, then
+
+    * We return a link or image node whose children are the inlines
+      after the text node pointed to by the opening delimiter.
+
+    * We run *process emphasis* on these inlines, with the `[` opener
+      as `stack_bottom`.
+
+    * We remove the opening delimiter.
+
+    * If we have a link (and not an image), we also set all
+      `[` delimiters before the opening delimiter to *inactive*.  (This
+      will prevent us from getting links within links.)
+
+#### *process emphasis*
+
+Parameter `stack_bottom` sets a lower bound to how far we
+descend in the [delimiter stack].  If it is NULL, we can
+go all the way to the bottom.  Otherwise, we stop before
+visiting `stack_bottom`.
+
+Let `current_position` point to the element on the [delimiter stack]
+just above `stack_bottom` (or the first element if `stack_bottom`
+is NULL).
+
+We keep track of the `openers_bottom` for each delimiter
+type (`*`, `_`), indexed to the length of the closing delimiter run
+(modulo 3) and to whether the closing delimiter can also be an
+opener.  Initialize this to `stack_bottom`.
+
+Then we repeat the following until we run out of potential
+closers:
+
+- Move `current_position` forward in the delimiter stack (if needed)
+  until we find the first potential closer with delimiter `*` or `_`.
+  (This will be the potential closer closest
+  to the beginning of the input -- the first one in parse order.)
+
+- Now, look back in the stack (staying above `stack_bottom` and
+  the `openers_bottom` for this delimiter type) for the
+  first matching potential opener ("matching" means same delimiter).
+
+- If one is found:
+
+  + Figure out whether we have emphasis or strong emphasis:
+    if both closer and opener spans have length >= 2, we have
+    strong, otherwise regular.
+
+  + Insert an emph or strong emph node accordingly, after
+    the text node corresponding to the opener.
+
+  + Remove any delimiters between the opener and closer from
+    the delimiter stack.
+
+  + Remove 1 (for regular emph) or 2 (for strong emph) delimiters
+    from the opening and closing text nodes.  If they become empty
+    as a result, remove them and remove the corresponding element
+    of the delimiter stack.  If the closing node is removed, reset
+    `current_position` to the next element in the stack.
+
+- If none is found:
+
+  + Set `openers_bottom` to the element before `current_position`.
+    (We know that there are no openers for this kind of closer up to and
+    including this point, so this puts a lower bound on future searches.)
+
+  + If the closer at `current_position` is not a potential opener,
+    remove it from the delimiter stack (since we know it can't
+    be a closer either).
+
+  + Advance `current_position` to the next element in the stack.
+
+After we're done, we remove all delimiters above `stack_bottom` from the
+delimiter stack.
diff --git a/tdemarkdown/md4c/test/spec_tests.py b/tdemarkdown/md4c/test/spec_tests.py
new file mode 100755
index 000000000..c739e5f9a
--- /dev/null
+++ b/tdemarkdown/md4c/test/spec_tests.py
@@ -0,0 +1,144 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+
+import sys
+from difflib import unified_diff
+import argparse
+import re
+import json
+from cmark import CMark
+from normalize import normalize_html
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(description='Run cmark tests.')
+    parser.add_argument('-p', '--program', dest='program', nargs='?', default=None,
+            help='program to test')
+    parser.add_argument('-s', '--spec', dest='spec', nargs='?', default='spec.txt',
+            help='path to spec')
+    parser.add_argument('-P', '--pattern', dest='pattern', nargs='?',
+            default=None, help='limit to sections matching regex pattern')
+    parser.add_argument('--library-dir', dest='library_dir', nargs='?',
+            default=None, help='directory containing dynamic library')
+    parser.add_argument('--no-normalize', dest='normalize',
+            action='store_const', const=False, default=True,
+            help='do not normalize HTML')
+    parser.add_argument('-d', '--dump-tests', dest='dump_tests',
+            action='store_const', const=True, default=False,
+            help='dump tests in JSON format')
+    parser.add_argument('--debug-normalization', dest='debug_normalization',
+            action='store_const', const=True,
+            default=False, help='filter stdin through normalizer for testing')
+    parser.add_argument('-n', '--number', type=int, default=None,
+            help='only consider the test with the given number')
+    args = parser.parse_args(sys.argv[1:])
+
+def out(str):
+    sys.stdout.buffer.write(str.encode('utf-8')) 
+
+def print_test_header(headertext, example_number, start_line, end_line):
+    out("Example %d (lines %d-%d) %s\n" % (example_number,start_line,end_line,headertext))
+
+def do_test(test, normalize, result_counts):
+    [retcode, actual_html, err] = cmark.to_html(test['markdown'])
+    if retcode == 0:
+        expected_html = test['html']
+        unicode_error = None
+        if normalize:
+            try:
+                passed = normalize_html(actual_html) == normalize_html(expected_html)
+            except UnicodeDecodeError as e:
+                unicode_error = e
+                passed = False
+        else:
+            passed = actual_html == expected_html
+        if passed:
+            result_counts['pass'] += 1
+        else:
+            print_test_header(test['section'], test['example'], test['start_line'], test['end_line'])
+            out(test['markdown'] + '\n')
+            if unicode_error:
+                out("Unicode error: " + str(unicode_error) + '\n')
+                out("Expected: " + repr(expected_html) + '\n')
+                out("Got:      " + repr(actual_html) + '\n')
+            else:
+                expected_html_lines = expected_html.splitlines(True)
+                actual_html_lines = actual_html.splitlines(True)
+                for diffline in unified_diff(expected_html_lines, actual_html_lines,
+                                "expected HTML", "actual HTML"):
+                    out(diffline)
+            out('\n')
+            result_counts['fail'] += 1
+    else:
+        print_test_header(test['section'], test['example'], test['start_line'], test['end_line'])
+        out("program returned error code %d\n" % retcode)
+        sys.stdout.buffer.write(err)
+        result_counts['error'] += 1
+
+def get_tests(specfile):
+    line_number = 0
+    start_line = 0
+    end_line = 0
+    example_number = 0
+    markdown_lines = []
+    html_lines = []
+    state = 0  # 0 regular text, 1 markdown example, 2 html output
+    headertext = ''
+    tests = []
+
+    header_re = re.compile('#+ ')
+
+    with open(specfile, 'r', encoding='utf-8', newline='\n') as specf:
+        for line in specf:
+            line_number = line_number + 1
+            l = line.strip()
+            #if l == "`" * 32 + " example":
+            if re.match("`{32} example( [a-z]{1,})?", l):
+                state = 1
+            elif state == 2 and l == "`" * 32:
+                state = 0
+                example_number = example_number + 1
+                end_line = line_number
+                tests.append({
+                    "markdown":''.join(markdown_lines).replace('→',"\t"),
+                    "html":''.join(html_lines).replace('→',"\t"),
+                    "example": example_number,
+                    "start_line": start_line,
+                    "end_line": end_line,
+                    "section": headertext})
+                start_line = 0
+                markdown_lines = []
+                html_lines = []
+            elif l == ".":
+                state = 2
+            elif state == 1:
+                if start_line == 0:
+                    start_line = line_number - 1
+                markdown_lines.append(line)
+            elif state == 2:
+                html_lines.append(line)
+            elif state == 0 and re.match(header_re, line):
+                headertext = header_re.sub('', line).strip()
+    return tests
+
+if __name__ == "__main__":
+    if args.debug_normalization:
+        out(normalize_html(sys.stdin.read()))
+        exit(0)
+
+    all_tests = get_tests(args.spec)
+    if args.pattern:
+        pattern_re = re.compile(args.pattern, re.IGNORECASE)
+    else:
+        pattern_re = re.compile('.')
+    tests = [ test for test in all_tests if re.search(pattern_re, test['section']) and (not args.number or test['example'] == args.number) ]
+    if args.dump_tests:
+        out(json.dumps(tests, ensure_ascii=False, indent=2))
+        exit(0)
+    else:
+        skipped = len(all_tests) - len(tests)
+        cmark = CMark(prog=args.program, library_dir=args.library_dir)
+        result_counts = {'pass': 0, 'fail': 0, 'error': 0, 'skip': skipped}
+        for test in tests:
+            do_test(test, args.normalize, result_counts)
+        out("{pass} passed, {fail} failed, {error} errored, {skip} skipped\n".format(**result_counts))
+        exit(result_counts['fail'] + result_counts['error'])
diff --git a/tdemarkdown/md4c/test/strikethrough.txt b/tdemarkdown/md4c/test/strikethrough.txt
new file mode 100644
index 000000000..884ce5983
--- /dev/null
+++ b/tdemarkdown/md4c/test/strikethrough.txt
@@ -0,0 +1,75 @@
+
+# Strike-Through
+
+With the flag `MD_FLAG_STRIKETHROUGH`, MD4C enables extension for recognition
+of strike-through spans.
+
+Strike-through text is any text wrapped in one or two tildes (`~`).
+
+```````````````````````````````` example
+~Hi~ Hello, world!
+.
+
Hi Hello, world!

+````````````````````````````````
+
+If the length of the opener and closer doesn't match, the strike-through is
+not recognized.
+
+```````````````````````````````` example
+This ~text~~ is curious.
+.
+
This ~text~~ is curious.

+````````````````````````````````
+
+Too long tilde sequence won't be recognized:
+
+```````````````````````````````` example
+foo ~~~bar~~~
+.
+
foo ~~~bar~~~

+````````````````````````````````
+
+Also note the markers cannot open a strike-through span if they are followed
+with a whitespace; and similarly, then cannot close the span if they are
+preceded with a whitespace:
+
+```````````````````````````````` example
+~foo ~bar
+.
+
~foo ~bar

+````````````````````````````````
+
+
+As with regular emphasis delimiters, a new paragraph will cause the cessation
+of parsing a strike-through:
+
+```````````````````````````````` example
+This ~~has a
+
+new paragraph~~.
+.
+
This ~~has a

+
new paragraph~~.

+````````````````````````````````
+
+
+## GitHub Issues
+
+### [Issue 69](https://github.com/mity/md4c/issues/69)
+```````````````````````````````` example
+~`foo`~
+.
+
foo

+````````````````````````````````
+
+```````````````````````````````` example
+~*foo*~
+.
+
foo

+````````````````````````````````
+
+```````````````````````````````` example
+*~foo~*
+.
+
foo

+````````````````````````````````
diff --git a/tdemarkdown/md4c/test/tables.txt b/tdemarkdown/md4c/test/tables.txt
new file mode 100644
index 000000000..b220f6685
--- /dev/null
+++ b/tdemarkdown/md4c/test/tables.txt
@@ -0,0 +1,357 @@
+
+# Tables
+
+With the flag `MD_FLAG_TABLES`, MD4C enables extension for recognition of
+tables.
+
+Basic table example of a table with two columns and three lines (when not
+counting the header) is as follows:
+
+```````````````````````````````` example
+| Column 1 | Column 2 |
+|----------|----------|
+| foo      | bar      |
+| baz      | qux      |
+| quux     | quuz     |
+.
+
+
+
+
+
+
+
+
+
+
Column 1Column 2
foobar
bazqux
quuxquuz

+````````````````````````````````
+
+The leading and succeeding pipe characters (`|`) on each line are optional:
+
+```````````````````````````````` example
+Column 1 | Column 2 |
+---------|--------- |
+foo      | bar      |
+baz      | qux      |
+quux     | quuz     |
+.
+
+
+
+
+
+
+
+
+
+
Column 1Column 2
foobar
bazqux
quuxquuz

+````````````````````````````````
+
+```````````````````````````````` example
+| Column 1 | Column 2
+|----------|---------
+| foo      | bar
+| baz      | qux
+| quux     | quuz
+.
+
+
+
+
+
+
+
+
+
+
Column 1Column 2
foobar
bazqux
quuxquuz

+````````````````````````````````
+
+```````````````````````````````` example
+Column 1 | Column 2
+---------|---------
+foo      | bar
+baz      | qux
+quux     | quuz
+.
+
+
+
+
+
+
+
+
+
+
Column 1Column 2
foobar
bazqux
quuxquuz

+````````````````````````````````
+
+However for one-column table, at least one pipe has to be used in the table
+header underline, otherwise it would be parsed as a Setext title followed by
+a paragraph.
+
+```````````````````````````````` example
+Column 1
+--------
+foo
+baz
+quux
+.
+
Column 1

+
foo
+baz
+quux

+````````````````````````````````
+
+Leading and trailing whitespace in a table cell is ignored and the columns do
+not need to be aligned.
+
+```````````````````````````````` example
+Column 1 |Column 2
+---|---
+foo | bar
+baz| qux
+quux|quuz
+.
+
+
+
+
+
+
+
+
+
+
Column 1Column 2
foobar
bazqux
quuxquuz

+````````````````````````````````
+
+The table cannot interrupt a paragraph.
+
+```````````````````````````````` example
+Lorem ipsum dolor sit amet.
+| Column 1 | Column 2
+| ---------|---------
+| foo      | bar
+| baz      | qux
+| quux     | quuz
+.
+
Lorem ipsum dolor sit amet.
+| Column 1 | Column 2
+| ---------|---------
+| foo      | bar
+| baz      | qux
+| quux     | quuz

+````````````````````````````````
+
+Similarly, paragraph cannot interrupt a table:
+
+```````````````````````````````` example
+Column 1 | Column 2
+---------|---------
+foo      | bar
+baz      | qux
+quux     | quuz
+Lorem ipsum dolor sit amet.
+.
+
+
+
+
+
+
+
+
+
+
+
Column 1Column 2
foobar
bazqux
quuxquuz
Lorem ipsum dolor sit amet.

+````````````````````````````````
+
+The first, the last or both the first and the last dash in each column
+underline can be replaced with a colon (`:`) to request left, right or middle
+alignment of the respective column:
+
+```````````````````````````````` example
+| Column 1 | Column 2 | Column 3 | Column 4 |
+|----------|:---------|:--------:|---------:|
+| default  | left     | center   | right    |
+.
+
+
+
+
+
+
+
+
Column 1Column 2Column 3Column 4
defaultleftcenterright

+````````````````````````````````
+
+To include a literal pipe character in any cell, it has to be escaped.
+
+```````````````````````````````` example
+Column 1 | Column 2
+---------|---------
+foo      | bar
+baz      | qux \| xyzzy
+quux     | quuz
+.
+
+
+
+
+
+
+
+
+
+
Column 1Column 2
foobar
bazqux | xyzzy
quuxquuz

+````````````````````````````````
+
+Contents of each cell is parsed as an inline text which may contents any
+inline Markdown spans like emphasis, strong emphasis, links etc.
+
+```````````````````````````````` example
+Column 1 | Column 2
+---------|---------
+*foo*    | bar
+**baz**  | [qux]
+quux     | [quuz](/url2)
+
+[qux]: /url
+.
+
+
+
+
+
+
+
+
+
+
Column 1Column 2
foobar
bazqux
quuxquuz

+````````````````````````````````
+
+However pipes which are inside a code span are not recognized as cell
+boundaries.
+
+```````````````````````````````` example
+Column 1 | Column 2
+---------|---------
+`foo     | bar`
+baz      | qux
+quux     | quuz
+.
+
+
+
+
+
+
+
+
+
+
Column 1Column 2
foo     | bar
bazqux
quuxquuz

+````````````````````````````````
+
+
+## GitHub Issues
+
+### [Issue 41](https://github.com/mity/md4c/issues/41)
+```````````````````````````````` example
+* x|x
+---|---
+.
+
    
+
  • x|x
+---|---
    • 
+

+````````````````````````````````
+(Not a table, because the underline has wrong indentation and is not part of the
+list item.)
+
+```````````````````````````````` example
+* x|x
+  ---|---
+x|x
+.
+
    
+
  • 
+
+
+
+
+
+
+
    xx
    
+
    • 
+

+
x|x

+````````````````````````````````
+(Here the underline has the right indentation so the table is detected.
+But the last line is not part of it due its indentation.)
+
+
+### [Issue 42](https://github.com/mity/md4c/issues/42)
+
+```````````````````````````````` example
+] http://x.x *x*
+
+|x|x|
+|---|---|
+|x|
+.
+
] http://x.x x

+
+
+
+
+
+
+
+
+
+
+
+
+
+
xx
x

+````````````````````````````````
+
+
+### [Issue 104](https://github.com/mity/md4c/issues/104)
+
+```````````````````````````````` example
+A | B
+--- | ---
+[x](url)
+.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
AB
x

+````````````````````````````````
+
+
+### [Issue 138](https://github.com/mity/md4c/issues/138)
+
+```````````````````````````````` example
+| abc | def |
+| --- | --- |
+.
+
+
+
+
+
+
+
+
abcdef

+````````````````````````````````
diff --git a/tdemarkdown/md4c/test/tasklists.txt b/tdemarkdown/md4c/test/tasklists.txt
new file mode 100644
index 000000000..aae1bf8eb
--- /dev/null
+++ b/tdemarkdown/md4c/test/tasklists.txt
@@ -0,0 +1,117 @@
+
+# Tasklists
+
+With the flag `MD_FLAG_TASKLISTS`, MD4C enables extension for recognition of
+task lists.
+
+Basic task list may look as follows:
+
+```````````````````````````````` example
+ * [x] foo
+ * [X] bar
+ * [ ] baz
+.
+
    
+
  • foo
    • 
+
  • bar
    • 
+
  • baz
    • 
+

+````````````````````````````````
+
+Task lists can also be in ordered lists:
+
+```````````````````````````````` example
+ 1. [x] foo
+ 2. [X] bar
+ 3. [ ] baz
+.
+
    
+
  1. foo
    2. 
+
  2. bar
    3. 
+
  3. baz
    4. 
+

+````````````````````````````````
+
+Task lists can also be nested in ordinary lists:
+
+```````````````````````````````` example
+ * xxx:
+   * [x] foo
+   * [x] bar
+   * [ ] baz
+ * yyy:
+   * [ ] qux
+   * [x] quux
+   * [ ] quuz
+.
+
    
+
  • xxx:
+
      
+
    • foo
      • 
+
    • bar
      • 
+
    • baz
      • 
+
    • 
+
  • yyy:
+
      
+
    • qux
      • 
+
    • quux
      • 
+
    • quuz
      • 
+
    • 
+

+````````````````````````````````
+
+Or in a parent task list:
+
+```````````````````````````````` example
+ 1. [x] xxx:
+    * [x] foo
+    * [x] bar
+    * [ ] baz
+ 2. [ ] yyy:
+    * [ ] qux
+    * [x] quux
+    * [ ] quuz
+.
+
    
+
  1. xxx:
+
      
+
    • foo
      • 
+
    • bar
      • 
+
    • baz
      • 
+
    2. 
+
  2. yyy:
+
      
+
    • qux
      • 
+
    • quux
      • 
+
    • quuz
      • 
+
    3. 
+

+````````````````````````````````
+
+Also, ordinary lists can be nested in the task lists.
+
+```````````````````````````````` example
+ * [x] xxx:
+   * foo
+   * bar
+   * baz
+ * [ ] yyy:
+   * qux
+   * quux
+   * quuz
+.
+
    
+
  • xxx:
+
      
+
    • foo
      • 
+
    • bar
      • 
+
    • baz
      • 
+
    • 
+
  • yyy:
+
      
+
    • qux
      • 
+
    • quux
      • 
+
    • quuz
      • 
+
    • 
+

+````````````````````````````````
diff --git a/tdemarkdown/md4c/test/underline.txt b/tdemarkdown/md4c/test/underline.txt
new file mode 100644
index 000000000..289e97fa1
--- /dev/null
+++ b/tdemarkdown/md4c/test/underline.txt
@@ -0,0 +1,39 @@
+
+# Underline
+
+With the flag `MD_FLAG_UNDERLINE`, MD4C sees underscore `_` rather as a mark
+denoting an underlined span rather than an ordinary emphasis (or a strong
+emphasis).
+
+```````````````````````````````` example
+_foo_
+.
+
foo

+````````````````````````````````
+
+In sequences of multiple underscores, each single one translates into an
+underline span mark.
+
+```````````````````````````````` example
+___foo___
+.
+
foo

+````````````````````````````````
+
+Intra-word underscores are not recognized as underline marks:
+
+```````````````````````````````` example
+foo_bar_baz
+.
+
foo_bar_baz

+````````````````````````````````
+
+Also the parser follows the standard understanding when the underscore can
+or cannot open or close a span. Therefore there is no underline in the following
+example because no underline can be seen as a closing mark.
+
+```````````````````````````````` example
+_foo _bar
+.
+
_foo _bar

+````````````````````````````````
diff --git a/tdemarkdown/md4c/test/wiki-links.txt b/tdemarkdown/md4c/test/wiki-links.txt
new file mode 100644
index 000000000..00d394e7f
--- /dev/null
+++ b/tdemarkdown/md4c/test/wiki-links.txt
@@ -0,0 +1,232 @@
+
+# Wiki Links
+
+With the flag `MD_FLAG_WIKILINKS`, MD4C recognizes wiki links.
+
+The simple wiki-link is a wiki-link destination enclosed in `[[` followed with
+`]]`.
+
+```````````````````````````````` example
+[[foo]]
+.
+
foo

+````````````````````````````````
+
+However wiki-link may contain an explicit label, delimited from the destination
+with `|`.
+
+```````````````````````````````` example
+[[foo|bar]]
+.
+
bar

+````````````````````````````````
+
+A wiki-link destination cannot be empty.
+
+```````````````````````````````` example
+[[]]
+.
+
[[]]

+````````````````````````````````
+
+```````````````````````````````` example
+[[|foo]]
+.
+
[[|foo]]

+````````````````````````````````
+
+
+The wiki-link destination cannot contain a new line.
+
+```````````````````````````````` example
+[[foo
+bar]]
+.
+
[[foo
+bar]]

+````````````````````````````````
+
+```````````````````````````````` example
+[[foo
+bar|baz]]
+.
+
[[foo
+bar|baz]]

+````````````````````````````````
+
+The wiki-link destination is rendered verbatim; inline markup in it is not
+recognized.
+
+```````````````````````````````` example
+[[*foo*]]
+.
+
*foo*

+````````````````````````````````
+
+```````````````````````````````` example
+[[foo|![bar](bar.jpg)]]
+.
+
bar

+````````````````````````````````
+
+With multiple `|` delimiters, only the first one is recognized and the other
+ones are part of the label.
+
+```````````````````````````````` example
+[[foo|bar|baz]]
+.
+
bar|baz

+````````````````````````````````
+
+However the delimiter `|` can be escaped with `/`.
+
+```````````````````````````````` example
+[[foo\|bar|baz]]
+.
+
baz

+````````````````````````````````
+
+The label can contain inline elements.
+
+```````````````````````````````` example
+[[foo|*bar*]]
+.
+
bar

+````````````````````````````````
+
+Empty explicit label is the same as using the implicit label; i.e. the verbatim
+destination string is used as the label.
+
+```````````````````````````````` example
+[[foo|]]
+.
+
foo

+````````````````````````````````
+
+The label can span multiple lines.
+
+```````````````````````````````` example
+[[foo|foo
+bar
+baz]]
+.
+
foo
+bar
+baz

+````````````````````````````````
+
+Wiki-links have higher priority than links.
+
+```````````````````````````````` example
+[[foo]](foo.jpg)
+.
+
foo(foo.jpg)

+````````````````````````````````
+
+```````````````````````````````` example
+[foo]: /url
+
+[[foo]]
+.
+
foo

+````````````````````````````````
+
+Wiki links can be inlined in tables.
+
+```````````````````````````````` example
+| A                | B   |
+|------------------|-----|
+| [[foo|*bar*]]    | baz |
+.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
AB
barbaz

+````````````````````````````````
+
+Wiki-links are not prioritized over images.
+
+```````````````````````````````` example
+![[foo]](foo.jpg)
+.
+
[foo]

+````````````````````````````````
+
+Something that may look like a wiki-link at first, but turns out not to be,
+is recognized as a normal link.
+
+```````````````````````````````` example
+[[foo]
+
+[foo]: /url
+.
+
[foo

+````````````````````````````````
+
+Escaping the opening `[` escapes only that one character, not the whole `[[`
+opener:
+
+```````````````````````````````` example
+\[[foo]]
+
+[foo]: /url
+.
+
[foo]

+````````````````````````````````
+
+Like with other inline links, the innermost wiki-link is preferred.
+
+```````````````````````````````` example
+[[foo[[bar]]]]
+.
+
[[foobar]]

+````````````````````````````````
+
+There is limit of 100 characters for the wiki-link destination.
+
+```````````````````````````````` example
+[[12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901]]
+[[12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901|foo]]
+.
+
[[12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901]]
+[[12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901|foo]]

+````````````````````````````````
+
+100 characters inside a wiki link target works.
+
+```````````````````````````````` example
+[[1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890]]
+[[1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890|foo]]
+.
+
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
+foo

+````````````````````````````````
+
+The limit on link content does not include any characters belonging to a block
+quote, if the label spans multiple lines contained in a block quote.
+
+```````````````````````````````` example
+> [[12345678901234567890123456789012345678901234567890|1234567890
+> 1234567890
+> 1234567890
+> 1234567890
+> 123456789]]
+.
+

+
1234567890
+1234567890
+1234567890
+1234567890
+123456789

+

+````````````````````````````````
diff --git a/translations/desktop_files/mimetypes/mimetypes.pot b/translations/desktop_files/mimetypes/mimetypes.pot
index c5e8ed0b3..94979da39 100644
--- a/translations/desktop_files/mimetypes/mimetypes.pot
+++ b/translations/desktop_files/mimetypes/mimetypes.pot
@@ -7,7 +7,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: PACKAGE VERSION\n"
 "Report-Msgid-Bugs-To: \n"
-"POT-Creation-Date: 2021-07-07 22:17+0000\n"
+"POT-Creation-Date: 2022-04-15 19:59+0200\n"
 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
 "Last-Translator: FULL NAME \n"
 "Language-Team: LANGUAGE \n"
@@ -1385,6 +1385,11 @@ msgstr ""
 msgid "HTML Document"
 msgstr ""
 
+#. Comment
+#: text/markdown.desktop:2
+msgid "Markdown document"
+msgstr ""
+
 #. Comment
 #: text/plain.desktop:3
 msgid "Plain Text Document"
diff --git a/translations/desktop_files/tdemarkdown-desktops/tdemarkdown-desktops.pot b/translations/desktop_files/tdemarkdown-desktops/tdemarkdown-desktops.pot
new file mode 100644
index 000000000..4825c35bc
--- /dev/null
+++ b/translations/desktop_files/tdemarkdown-desktops/tdemarkdown-desktops.pot
@@ -0,0 +1,27 @@
+# SOME DESCRIPTIVE TITLE.
+# This file is put in the public domain.
+# FIRST AUTHOR , YEAR.
+#
+#, fuzzy
+msgid ""
+msgstr ""
+"Project-Id-Version: PACKAGE VERSION\n"
+"Report-Msgid-Bugs-To: \n"
+"POT-Creation-Date: 2022-04-15 14:26+0200\n"
+"PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
+"Last-Translator: FULL NAME \n"
+"Language-Team: LANGUAGE \n"
+"Language: \n"
+"MIME-Version: 1.0\n"
+"Content-Type: text/plain; charset=UTF-8\n"
+"Content-Transfer-Encoding: 8bit\n"
+
+#. Name
+#: markdown_part.desktop:2
+msgid "Markdown Viewer"
+msgstr ""
+
+#. Comment
+#: markdown_part.desktop:4
+msgid "Embeddable lightweight markdown viewing component"
+msgstr ""
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