Some symbols are not rendered

[vivek-shadija]

Issue: Below mentioned 4 math commands are not recognized by mathjax and they are not rendered.

1. \parallelogram
2. \overarc{x}
3. \questeq
4. \longdiv{x}

[dpvc]

First, you have filed this issue in the wrong place. As the issue template indicates, this issue tracker is only for structural problems with the source code repository, not for general MathJax issues, which should be filed here. Don't just erase the information given in the issue template and ignore it.

I am transferring this issue to the proper issue tracker.

[dpvc]

Not every LaTeX command is implemented in MathJax, and none of these is. You can find a list of the commands that are available in the documentation. You don't indicate which version of MathJax you are using, so I've pointed to the v3 documentation.

For \parallelogram you could use \unicode{x25B1}, and could do \newcommand{\parallelogram}{\unicode{0x25B1}} to define \parallelogram to produce that.

For \overarc perhaps the best substitute is \overparen, and you can do \let\overarc=\overparen to define \overarc to produce that.

For \questeq you could use \stackrel{?}{=} and could do \newcommand{\questeq}{\stackrel{?}{=}} to define \questeq to equal that.

These three could be added to your MathJax configuration as described in the documentation.

The \longdiv macro is more challenging. If you are looking for \longdiv{num}{den} where num and den are integers, then there is an old v2 implementation here. For v4, I worked up a configuration that implements it:

MathJax = {
  tex: {
    packages: {'[+]': ['longdiv']}   
  },
  startup: {
    ready() {
      const {Configuration} = MathJax._.input.tex.Configuration;
      const {CommandMap} = MathJax._.input.tex.TokenMap;
      const TexError = MathJax._.input.tex.TexError.default;
      const TexParser = MathJax._.input.tex.TexParser.default;
      
      new CommandMap('longdiv', {
        longdiv: 'LongDiv'
      }, {
        LongDiv(parser, name) {
          const num = parser.GetArgument(name);
          const den = parser.GetArgument(name);
          if (!num.match(/^\d+$/) || !den.match(/^\d+/)) {
            throw new TexError('LONGDIV:NumDen', 'Numerator and denominator of %1 must be positive integers', name);
          }
          const n = parseInt(num);
          const d = parseInt(den);
          const q = Math.floor(n / d);
          let m = n;
          const tex = [
            '\\begin{array}[t]{r}',
            `${q} \\kern.2em \\\\[-3px]`,
            `${d}\\kern.1em \\enclose{longdiv}{\\kern.075em ${n}} \\\\[-4px]`
          ];
          const digits = String(q).split('');
          while (digits.length) {
            const digit = parseInt(digits.shift() + digits.join('').replace(/./g, '0'));
            if (digit === 0) continue;
            const p = d * digit;
            m -= p;
            tex.push(
              `\\underline{\\kern .2em ${p}\\Space{.2em}{0em}{.125em}} \\\\[-3px]`,
              `${m}\\Space{.2em}{0em}{.125em} \\\\[-4px]`
            );
          }
          tex.push('\\end{array}');
          parser.Push(new TexParser(tex.join('\n'), parser.stack.env, parser.configuration).mml());
        }
      });
      
      Configuration.create('longdiv', {
        handler: {
          macro: ['longdiv']
        }
      });
      
      MathJax.startup.defaultReady();
    }
  }
};

If you are using v3, this should also work there, with one change: TokenMap should be changed to SymbolMap in the second line of the ready() function.