Scheme Program Intervals

SPEND YOUR MONEY

This program assumes wages are earned and learned. See previous program on calculating wages and taxes.

DATA ANALYSIS
;;cost: number -> number
;;compute cost with a discount of 10% on first $100, 15% on next 400,
;; 25% on next 500, 50% on any amount spent over 1000.
(define (cost $)

EXAMPLES
(cost 50) = 45 (cost 100) = 90 (cost 200) = 175 (cost 500) = 430
(cost 600) = 500 (cost 1000) = 800 (cost 2000) = (+ 800 500) = 1300

BODY

Template

? Conditional Expressions ?

Answers

(cond
   [         ]
   [         ]
   [         ] 
   [         ])

(<= $ 100)
(and (> $ 100) (<= $ 500))
(and (> $ 500) (<= $ 1000))
(> $ 1000)

(discount 10 $)

(+ (discount 10 100)
   (discount 15 (- $ 100)))

(+ (discount 10 100)
   (discount 15 400)
   (discount 25 (- $ 500)))

(+ (discount 10 100)
   (discount 15 400)
   (discount 25 500)
   (discount 50 (- $ 1000)))

Interaction Window

Welcome to DrScheme, 
version 100.
Language: Beginner.
45
=
45
90
=
90
175
=
175
430
=
430
505
=
500
805
=
800
1305
=
1300
=
1300

Definition Window

;;discount: number number -> number
;helper function to compute percentage decrease
(define (discount percent money)
  (- money (* money (/ percent 100))))

;;cost: number -> number
;;compute cost with a discount of 10% on first $100, 15% on next 400,
;;    25% on next 500, 50% on any amount spent over 1000.
(define (cost $)
  (cond
    [(<= $ 100)  (discount 10 $)]
    [(<= $ 500)  (+ (discount 10 100)
                    (discount 15 (- $ 100)))]
    [(<= $ 1000) (+ (discount 10 100)
                    (discount 15 400)
                    (discount 25 (- $ 500)))]
    [(> $ 1000)  (+ (discount 10 100)
                    (discount 15 400)
                    (discount 25 500)
                    (discount 50 (- $ 1000)))]))

(cost 50)  = 45
(cost 100) = 90
(cost 200) = 175
(cost 500) = 430
(cost 600) = 500
(cost 1000) = 800
(cost 2000) = 1300

INVEST YOUR MONEY

Instead of spending your money, try investing your money. The only difference is:

the percentage rates are lower

and a percentage increase helper program is used which adds instead of subtracts.

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