Function intFracPart

src/compute-engine/rubi/rubi-utils.ts:4239–4258

(
  u: Expression,
  ce: ComputeEngine,
  part: 'int' | 'frac'
)

        : ce.function('Multiply', scalars);
  let atoms: TrigAtom[] = [{ coef: ce.One, kind: null, arg: ce.One }];
  for (const t of trigFactors) atoms = mulAtomsByTrig(ce, atoms, t.head, t.arg);
  // fold the term scalar into every atom's coefficient
  return atoms.map((a) => ({
    coef: scalar.isSame(1) ? a.coef : ce.function('Multiply', [scalar, a.coef]),
    kind: a.kind,
    arg: a.arg,
  }));
}

/** Materialize a list of trig atoms as a canonical Add. */
function atomsToExpr(ce: ComputeEngine, atoms: TrigAtom[]): Expression {
  const terms = atoms.map((a) =>
    a.kind === null
      ? a.coef
      : ce.function('Multiply', [a.coef, ce.function(a.kind, [a.arg])])
  );
  if (terms.length === 0) return ce.Zero;
  if (terms.length === 1) return terms[0];
  return ce.function('Add', terms);
}

/** ExpandTrigReduce for circular Sin/Cos: product-to-sum into a real-trig
 *  linear combination. `deepExpand` first distributes products and expands