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commonmark

High Performance CommonMark and Github Markdown Rendering in R

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The CommonMark specification defines a rationalized version of markdown syntax. This package uses the ‘cmark’ reference implementation for converting markdown text into various formats including html, latex and groff man. In addition it exposes the markdown parse tree in xml format. The latest version of this package also adds support for Github extensions including tables, autolinks and strikethrough text.

Documentation

Basic Markdown 

library(commonmark)
md <- "## Test
An *example* text for the `commonmark` package."

# Convert to Latex
cat(markdown_latex(md))
\subsection{Test}

An \emph{example} text for the \texttt{commonmark} package.
# Convert to HTML
cat(markdown_html(md))
<h2>Test</h2>
<p>An <em>example</em> text for the <code>commonmark</code> package.</p>
# Convert to 'groff' man 
cat(markdown_man(md))
.SS
Test
.PP
An \f[I]example\f[] text for the \f[C]commonmark\f[] package.
# Convert back to (normalized) markdown
cat(markdown_commonmark(md))
## Test

An *example* text for the `commonmark` package.
# The markdown parse tree
cat(markdown_xml(md))
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE document SYSTEM "CommonMark.dtd">
<document xmlns="http://commonmark.org/xml/1.0">
  <heading level="2">
    <text>Test</text>
  </heading>
  <paragraph>
    <text>An </text>
    <emph>
      <text>example</text>
    </emph>
    <text> text for the </text>
    <code>commonmark</code>
    <text> package.</text>
  </paragraph>
</document>

Github Extensions

Commonmark includes several ‘extensions’ to enable features which are not (yet) part of the official specification. The current version of the commonmark R package offers 4 such extensions:

  • table support rendering of tables
  • strikethough via ~sometext~ syntax
  • autolink automatically turn URLs into hyperlinks
  • tagfilter blacklist html tags: title textarea style xmp iframe noembed noframes script plaintext.
  • tasklist turns certain list items into checkboxes

These extensions were added by Github to support GitHub Flavored Markdown.

table <- '
aaa | bbb | ccc | ddd | eee
:-- | --- | :-: | --- | --:
fff | ggg | hhh | iii | jjj'

cat(markdown_latex(table, extensions = TRUE))
\begin{table}
\begin{tabular}{llclr}
aaa & bbb & ccc & ddd & eee \\
fff & ggg & hhh & iii & jjj \\
\end{tabular}
\end{table}
cat(markdown_html(table, extensions = TRUE))
<table>
<thead>
<tr>
<th align="left">aaa</th>
<th>bbb</th>
<th align="center">ccc</th>
<th>ddd</th>
<th align="right">eee</th>
</tr>
</thead>
<tbody>
<tr>
<td align="left">fff</td>
<td>ggg</td>
<td align="center">hhh</td>
<td>iii</td>
<td align="right">jjj</td>
</tr></tbody></table>