Function assign

src/compute-engine/rubi/match.ts:208–236

(i: number)

// Orderless + flat matching for Add/Multiply.
//
// Pattern operands are ordered deterministic-first (var, const, node,
// slots last) and assigned to expression operands by backtracking.
// Optional slots may bind their default instead of consuming an operand.
// The FINAL pattern operand, when it is a slot, absorbs all remaining
// expression operands ("u_. absorbs the rest of the product").
function mAC(
  pat: { op: string; ops: Pat[] },
  expr: Expression,
  x: Expression,
  env: Env,
  k: () => boolean
): boolean {
  const exprOps = expr.ops!;
  const rank = (p: Pat): number =>
    p.kind === 'var'
      ? 0
      : p.kind === 'const'
        ? 1
        : p.kind === 'node'
          ? 2
          : p.kind === 'slot'
            ? 3
            : 4;
  const ordered = [...pat.ops].sort((a, b) => rank(a) - rank(b));

  const used = new Array<boolean>(exprOps.length).fill(false);
  const ce = expr.engine;

  const assign = (i: number): boolean => {
    if (i === ordered.length) return used.every(Boolean) && k();
    const p = ordered[i];