Arithmetic from Addition

The Challenge

Write methods to implement addition, subtraction and division using only addition.

The Solution

function multiply(x, y) {
  z = 0;
  for(i = 0; i < y; i++) {
    z +=x;
  }
  return z;
}

function negate(x) {
  y = 0;
  a = x < 0 ? 1 : -1;
  for(i = 0; i < x; i++) {
    y += a;
  }
  return y;
}

function subtract(x,fromY) {
  return fromY + negate(x);
}

function divide(x, byY) {
  r = 0;
  s = 0;
  while(s < x) {
    r += 1;
    s += byY;
  }
  return r;
}