Why use `cmark` and not X?
==========================

`hoedown`
---------

`hoedown` (which derives from `sundown`) is slightly faster
than `cmark` in our benchmarks (0.21s vs. 0.29s).  But both
are much faster than any other available implementations.

`hoedown` boasts of including "protection against all possible
DOS attacks," but there are some chinks in the armor:

    % time python -c 'print(("[" * 50000) + "a" + ("]" * 50000))' | cmark
    ...
    user 0m0.073s
    % time python -c 'print(("[" * 50000) + "a" + ("]" * 50000))' | hoedown
    ...
    0m17.84s

`hoedown` has many parsing bugs.  Here is a selection:

    % hoedown
    - one
      - two
        1. three
    ^D
    <ul>
    <li>one

    <ul>
    <li>two</li>
    <li>three</li>
    </ul></li>
    </ul>


    % hoedown
    ## hi\###
    ^D
    <h2>hi\</h2>


    % hoedown
    [ΑΓΩ]: /φου

    [αγω]
    ^D
    <p>[αγω]</p>


    % hoedown
    ```
    [foo]: /url
    ```

    [foo]
    ^D
    <p>```</p>

    <p>```</p>

    <p><a href="/url">foo</a></p>


    % hoedown
    [foo](url "ti\*tle")
    ^D
    <p><a href="url" title="ti\*tle">foo</a></p>


`discount`
----------

`cmark` is about six times faster.

`kramdown`
----------

`cmark` is about a hundred times faster.

`kramdown` also gets tied in knots by pathological input like

    python -c 'print(("[" * 50000) + "a" + ("]" * 50000))'