Function sumSimplerAuxQ

src/compute-engine/rubi/rubi-utils.ts:519–530

Rubi SumSimplerAuxQ — recursion over (expanded) sum terms: * - v a sum: every term of v is rational or aux-simpler wrt u * - u a sum: some term of u is aux-simpler wrt v * - both terms: v ≠ 0, same non-numeric factors, and the numeric-factor * ratio nf(u)/nf(v) < −1/2 (or = −1/2 with nf(u) < 0

(u: Expression, v: Expression)

function ratParts(e: Expression): [number, number] | null {
  if (!isLiteralRational(e)) return null;
  const num = e.numerator.re;
  const den = e.denominator.re;
  if (typeof num !== 'number' || typeof den !== 'number') return null;
  return [num, den];
}

/** Rubi NumericFactor/NonnumericFactors split of a term: the leading
 * rational coefficient and the remaining (non-numeric) factors. */
function splitNumericFactor(u: Expression): {
  coef: number;
  rest: Expression;
} {
  const ce = u.engine;
  const r = ratParts(u);
  if (r) return { coef: r[0] / r[1], rest: ce.One };