Parsedown: sub/superscript

Question

The current version of Parsedown 1.8.0-beta-5 doesn't have a builtin syntax for sub/superscript. Although CommonMark doesn't specify such syntax, several other lightweight markup languages (ex: Parsedown Extreme, Textile) use a syntax similar to the following:

in: 19^th^  
out: 19<sup>th</sup>

in: H~2~O  
out: H<sub>2</sub>O

Question
What steps should be taken in order to modify Parsedown.php file and include such syntax?

Note: This issue has already come up other times (Parsedown, add sub/superscript). However, there is still no step-by-step guide explaining what modifications should be done in Parsedown.php file in order to achieve that.

Mark Messa · Accepted Answer · 2018-08-21T23:24:49.857

Append Superscript and Tilde in $InlineTypes:

protected $InlineTypes = array(
    '!' => array('Image'),
    '&' => array('SpecialCharacter'),
    '*' => array('Emphasis'),
    ':' => array('Url'),
    '<' => array('UrlTag', 'EmailTag', 'Markup'),
    '[' => array('Link'),
    '_' => array('Emphasis'),
    '`' => array('Code'),
    '~' => array('Tilde'),
    '^' => array('Superscript'),
    '\\' => array('EscapeSequence'),
);

Define methods inlineSuperscript. It should look pretty much like inlineStrikethrough:

protected function inlineSuperscript($Excerpt)
{
    if (preg_match('/^\^(.+?)\^/', $Excerpt['text'], $matches))
    {
        return array(
            'extent' => strlen($matches[0]),
            'element' => array(
                'name' => 'sup',
                'handler' => array(
                    'function' => 'lineElements',
                    'argument' => $matches[1],
                    'destination' => 'elements',
                )
            ),
        );
    }
}

Define methods inlineTilde and delete method inlineStrikethrough. It should look pretty much like inlineEmphasis:

protected function inlineTilde($Excerpt)
{
    if ( ! isset($Excerpt['text'][1]))
    {
        return;
    }

    $marker = $Excerpt['text'][0];

    if ($Excerpt['text'][1] === $marker and preg_match('/^~~(?=\S)(.+?)(?<=\S)~~/', $Excerpt['text'], $matches))
    {
        $emphasis = 'del';
    }
    elseif (preg_match('/^~(?=\S)(.+?)(?<=\S)~/', $Excerpt['text'], $matches))
    {
        $emphasis = 'sub';
    }
    else
    {
        return;
    }

    return array(
        'extent' => strlen($matches[0]),
        'element' => array(
            'name' => $emphasis,
            'handler' => array(
                'function' => 'lineElements',
                'argument' => $matches[1],
                'destination' => 'elements',
            )
        ),
    );
}

Add the new symbol to $inlineMarkerList:

protected $inlineMarkerList = '!*_&[:<`~\\^';

Parsedown: sub/superscript

1 Answers1