Function apply

src/compute-engine/boxed-expression/apply.ts:90–117

(
  expr: Expression,
  fn: (x: number) => number | Complex,
  bigFn?: (x: BigDecimal) => BigDecimal | Complex | number,
  complexFn?: (x: Complex) => number | Complex
)

  numericApproximation: boolean | undefined,
  ...ops: ReadonlyArray<Expression | undefined | null>
): boolean {
  if (numericApproximation) return true;
  return ops.some((op) => op != null && !isExactNumber(op));
}

/**
 * True if a kernel result is `undefined` or a NaN number/Complex/BigDecimal —
 * the signal that the value is "outside this kernel's implemented (real)
 * domain", used to trigger a cascade to a complex-valued kernel. A boxed
 * `Expression` result is never a domain signal and never cascades.
 */
function isNaNKernelResult(r: unknown): boolean {
  if (r === undefined) return true;
  if (typeof r === 'number') return Number.isNaN(r);
  if (r instanceof Complex) return r.isNaN();
  if (r instanceof BigDecimal) return r.isNaN();
  return false;
}

export function apply(
  expr: Expression,
  fn: (x: number) => number | Complex,
  bigFn?: (x: BigDecimal) => BigDecimal | Complex | number,
  complexFn?: (x: Complex) => number | Complex
): Expression | undefined {
  if (!isNumber(expr)) return undefined;
  const ce = expr.engine;

  let result: number | Complex | BigDecimal | undefined = undefined;
  if (expr.im !== 0) result = complexFn?.(ce.complex(expr.re, expr.im));
  else {