Function isSpecialHeaded

scripts/fungrim/compile-rules.ts:725–729

(side: MathJSON)

  'Hold',
]);

function isSpecialHeaded(side: MathJSON): boolean {
  return (
    Array.isArray(side) && typeof side[0] === 'string' && !CORE_HEADS.has(side[0])
  );
}

/** A match of the form `[Head, _w1, _w2, …]` (distinct bare wildcards only):