Budgeting with discretionary income can be difficult because its hard when faced with daily decisions to think of that rather larger monthly figure in daily terms. This program helps you take your monthly discretionary money and turn it into a number you can target daily.

DailyAllowance.scala

object DailyAllowance extends App {

	val DaysInMonth = 30
	val MonthlyNet = USD("$5000.00")
	val MonthlyFixedExpenses = USD("$3000.00")

	case class Money(rate: Int)
	
	class USD(val dollars: Int, val cents: Int) extends Money(100) {
		val amountInCents = (dollars * rate) + cents
	
		def convertAmount(amount: Int): USD = {
			val dollars: Int = amount / rate
			val cents: Int = amount - (dollars * rate)
			new USD(dollars, cents)
		}
		
		def +(other: USD) = {
			convertAmount(this.amountInCents + other.amountInCents)
		}
		
		def -(other: USD) = {
			convertAmount(Math.abs(this.amountInCents - other.amountInCents))
		}
		
		def /(other: USD) = {
			convertAmount(this.amountInCents / other.amountInCents)
		}
		
		def /(x: Int) = {
			convertAmount(this.amountInCents / x)
		}
		
		override def toString(): String = {
			s"$$${dollars}.${if(cents < 10) "0" else ""}${cents}"
		}
	}
	
	object USD {
		def apply(s: String) = {
			val withoutDollarSign = if(s.charAt(0) == '$') s.substring(1) else s
			val Array(dollars,cents) = withoutDollarSign.split('.')
			if(cents.length > 2) {
				throw new IllegalArgumentException("Unrecognized format. Please use a format like $XXXX.XX or XXXX.XX.")
			}
			new USD(dollars.toInt, cents.toInt)
		}
	}

	println(s"Monthly net income: ${MonthlyNet}")
	println(s"Monthly fixed expenses: ${MonthlyFixedExpenses}")
	val remainingAfterExpenses = MonthlyNet - MonthlyFixedExpenses
	println(s"Discretionary income: ${remainingAfterExpenses}")
	println(s"Discretionary per day: ${remainingAfterExpenses / DaysInMonth}")
}