Function parse

src/compute-engine/latex-syntax/parse.ts:3231–3275

(
  latex: string,
  dictionary: IndexedLatexDictionary,
  options: Readonly<ParseLatexOptions>
)

    const start = this.index;
    // Skip visual space (e.g. `\ `, `\,`) before peeking postfix triggers, so
    // a `\{…\}` When-restriction can attach even when separated from its base
    // by space. Restricted to brace triggers: for other postfix operators —
    // notably `\left[…\right]` indexing — a preceding space means implicit
    // multiplication by a list literal (Desmos semantics), not a postfix.
    // The `this.index = start` no-match restore rolls back the skipped space.
    this.skipVisualSpace();
    if (this.index !== start) {
      const tok = this._tokens[this.index];
      const isBraceTrigger =
        tok === '\\{' ||
        (tok === '\\left' && this._tokens[this.index + 1] === '\\{');
      if (!isBraceTrigger) this.index = start;
    }
    const afterSpace = this.index;
    for (const [def, n] of this.peekDefinitions('postfix')) {
      this.index = afterSpace + n;
      const result = def.parse(this, lhs, until);
      if (result !== null) return result;
    }
    this.index = start;
    return null;
  }

  /**
   * This method can be invoked when we know we're in an error situation,
   * for example when there are tokens remaining after we've finished parsing.
   *
   * In general, if a context does not apply, we return `null` to give
   * the chance to some other option to be considered. However, in some cases
   * we know we've exhausted all possibilities, and in this case this method
   * will return an error expression as informative as possible.
   *
   * We've encountered a LaTeX command or symbol but were not able to match it
   * to any entry in the LaTeX dictionary, or ran into it in an unexpected
   * context (postfix operator lacking an argument, for example)
   */
  parseSyntaxError(): MathJsonExpression {
    const start = this.index;

    //
    // Is this an unexpected operator?
    // (this is an error handling code path)
    //
    // '^' is a special infix operator, with a custom parser
    if (this.peek === '^') {
      this.index += 1;
      return [