modulo_cashier.py

#!/usr/bin/env python

def check(s):
  if isinstance(s, int) or isinstance(s, float): return s
  exit()

def pluralize(currency, amount):
  if amount == 1: return currency
  if currency == "penny":
    return "pennies"
  else:
    return currency + "s"


def calculate(amount_due, amount_received):
  coins = { 1.0: 'dollar', 0.25: 'quarter', 0.1: 'dime', 0.05: 'nickel', 0.01: 'penny' }
  change = amount_received - amount_due
  print "Change: $%.2f" % change
  for value in reversed(sorted(coins.keys())):
    quantity_of_coin = change // value
    change -= quantity_of_coin * value
    print "%d %s" % (quantity_of_coin, pluralize(coins[value], quantity_of_coin))

amount_due = None
amount_received = None
while True:
  amount_due      = check(input("Amount Due:\t $"))
  amount_received = check(input("Amount Received: $"))
  calculate(amount_due, amount_received)

loop { [($amount_due = [(print "Amount Due:\t $"), eval(gets.strip)].last), ($amount_received = [(print "Amount Received: $"), eval(gets.strip)].last), ([(puts "Change: #{(change = $amount_due - $amount_received).round(2)}"), ({ 1.0 => 'dollar', 0.25 => 'quarter', 0.1 => 'dime', 0.05 => 'nickel', 0.01 => 'penny' }.each { |value, currency| [(change -= (quantity_of_coin = (change / value).floor) * value), (puts "#{quantity_of_coin} #{quantity_of_coin == 1 ? currency : currency == "penny" ? "pennies" : currency + "s"}")] })])] }