Function monoClassesX

src/compute-engine/rubi/rubi-utils.ts:1598–1613

group the structural sum terms of u into (exponent → summed coefficient) * classes; null when some term is not a structural monomial in x

(
  u: Expression,
  x: string
)

  const ops = u.ops;
  if (!ops) return null;
  switch (u.operator) {
    case 'Power': {
      if (ops[1].has(x)) return null;
      if (ops[0].symbol === x) return { coef: ce.One, exp: ops[1] };
      const k = realNum(ops[1]);
      if (k !== null && Number.isInteger(k)) {
        const m = monoPartsX(ops[0], x);
        if (m !== null)
          return {
            coef: m.coef.pow(k).evaluate(),
            exp: m.exp.mul(k).evaluate(),
          };
      }
      return null;
    }
    case 'Sqrt':
      if (ops[0].symbol === x)
        return { coef: ce.One, exp: ce.expr(['Rational', 1, 2]) };
      return null;