Function powers

src/compute-engine/boxed-expression/expand.ts:49–57

(n: number, exp: number)

}

// Return all the combinations of n non-negative integers that sum to exp.
function* powers(n: number, exp: number): Generator<number[]> {
  if (n === 1) {
    yield [exp];
    return;
  }

  for (let i = 0; i <= exp; i += 1)
    for (const p of powers(n - 1, exp - i)) yield [i, ...p];
}

/** Use the multinomial theorem (https://en.wikipedia.org/wiki/Multinomial_theorem) to expand the expression.