exports.add = function (a, b) {
  a = parseInt(a)
  b = parseInt(b)
  return a + b
}

exports.multiply = function * (a = 0, b = 0) {
  return a * b
}

exports.pow = function (a = 0) {
  return a * a
}
exports.div = function (a, b) {
  b = b || this.b
  return a / b
}