Function primary

src/math-json/parse-sympy.ts:331–353

(
  s: string,
  start: number
)

function primary(
  s: string,
  start: number
): [index: number, result: Expression | null] {
  // Attribute references, subscriptions, slices, and calls are not supported;
  // only atoms are recognized here.

  // eslint-disable-next-line prefer-const
  let [i, e] = atom(s, start);
  if (e) return [i, e];

  // subscription, slice, call attribute reference (x[i], x[a:b], x(a), x.a)
  if (e !== null && s[i] === '(') {
    if (symbol(e)) {
      let args: Expression[];
      [i, args] = expressionList(s, i);
      if (s[i] === ')') {
        return [i, [symbol(e), ...args] as Expression];
      }
    }
  }

  return [start, null];
}

function expression(
  s: string,