PRO CHANGE, payment, purchase, money
; 
;This will calculate the change and tender
; to be returned to the customer
;
; calculate change
return0=payment-purchase
change1=return0

;calculate Twenties
return1=return0 MOD 20.
twenty=(return0-return1)/20.

;calculate Tens
return2=return1 MOD 10
ten=(return1-return2)/10.

;calculate 5's
return3=return2 MOD 5
five=(return2-return3)/5.

;calculate 1s
return4=return3 MOD 1
one=(return3-return4)/1.

;calculate quarters
return6=return4 MOD .25
quarter=(return4-return6)/0.25

;calculate dimes
return7=return6 MOD .1
dime=(return6-return7)/.1

;calculate nickels
return8=return7 MOD .05
nickel=(return7-return8)/0.05

;calculate pennies - the +0.001 makes the Integer print work
; a value of 2 pennies would not return the correct amount
; as an integer display, so it has to be slightly larger.

penny=(return8)/0.01+.001

money=[change1, twenty, ten, five, one,	quarter, dime, nickel, penny]
;PRINT, money[8], money[8]+.001, format='(f6.2, i6)'

END

;**************************main program********************************

PRO idl_hw03_acp
;
;This will allow for calculation of change. Just execute the program 
; and feed in the input
;
PRINT, 'Please enter the purchase amount (<$200) '
READ, purchase

PRINT, 'Please enter the payment'
READ, payment
;
;This is the logic part for 3 cases
;1. Insufficient funds
;2. Exact Change
;3. Change coming 
; (and the bonus feature - it's a gas)
;
IF payment LT purchase THEN BEGIN
; Insufficient funds
	PRINT, 'Insufficient Funds', 'You owe', ABS(payment-purchase), FORMAT='(a,/,a,"  $",F6.2)'
ENDIF ELSE BEGIN
; If there is enough money
	CHANGE, payment, purchase, money
	IF money[0] EQ 0 THEN BEGIN
; Exact change
		PRINT, 'No Change Coming',  FORMAT='(a)'
	ENDIF ELSE BEGIN
; This is if there is change
		IF money[0] GT 0 THEN PRINT, 'Your change is $', money[0], FORMAT='(a, F6.2)'
		IF money[1] GT 0 THEN PRINT, money[1], '20s', FORMAT='(I6,"  ", a)'; twenties
		IF money[2] GT 0 THEN PRINT, money[2], '10s', FORMAT='(I6,"  ", a)'; tens
		IF money[3] GT 0 THEN PRINT, money[3], '5s', FORMAT='(I6,"  ", a)'; fives
		IF money[4] GT 0 THEN PRINT, money[4], '1s', FORMAT='(I6,"  ", a)'; ones
		IF money[5] GT 0 THEN PRINT, money[5], 'Quarters', FORMAT='(I6,"  ", a)'; Quarters
		IF money[6] GT 0 THEN PRINT, money[6], 'Dimes', FORMAT='(I6,"  ", a)'; Dimes
		IF money[7] GT 0 THEN PRINT, money[7], 'Nickels', FORMAT='(I6,"  ", a)'; Nickels
		IF money[8] GT 0 THEN PRINT, money[8], 'Pennies', FORMAT='(I6,"  ", a)'; Pennies
	ENDELSE
	PRINT, 'Just a bonus, you can buy', money[0]/3.959, $
		' gallons of gas on Saturday with your change.', FORMAT='(a,F7.3,a)'
ENDELSE
;
;
END