code: func add(a, b, carry int32) (int32, int32) {
  	sum := a + b + carry
  	if sum >= wordBase {
  		carry = 1
  		sum -= wordBase
  	} else {
  		carry = 0
  	}
  	return sum, carry
  }
docs: // add adds a and b and carry, returns the sum and new carry.