Function mul

src/compute-engine/rubi/normal-form.ts:62–72

(ce: ComputeEngine, fs: Expression[])

}

function mul(ce: ComputeEngine, fs: Expression[]): Expression {
  let flat = fs.flatMap(factors).filter((f) => !f.isSame(1));
  // WL Times auto-evaluation, which the Rubi corpus assumes:
  // 0·u → 0, and same-base power collection (d·d → d², u^a·u^b → u^(a+b))
  if (flat.some((f) => f.isSame(0))) return ce.Zero;
  flat = collectPowers(ce, flat);
  flat = collectSameExponent(ce, flat);
  if (flat.length === 0) return ce.One;
  if (flat.length === 1) return flat[0];
  return ce._fn('Multiply', flat);
}

/** Fuse factors sharing a NON-NUMERIC exponent: aˣ·bˣ → (a·b)ˣ. Sound for the
 * Rubi verification regime (positive-real parameters), and needed so a product