1 ;; The first three lines of this file were inserted by DrScheme. They record metadata
2 ;; about the language level of this file in a form that our tools can easily process.
3 #reader(lib "htdp-intermediate-reader.ss" "lang")((modname |23.1|) (read-case-sensitive #t) (teachpacks ((lib "draw.ss" "teachpack" "htdp") (lib "arrow.ss" "teachpack" "htdp") (lib "gui.ss" "teachpack" "htdp"))) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ((lib "draw.ss" "teachpack" "htdp") (lib "arrow.ss" "teachpack" "htdp") (lib "gui.ss" "teachpack" "htdp")))))
4 ;;Model
5 
6 ;build-number : (listof number) -> number
7 ;Given alon which represent the digits of a number, with the first digit representing the most significant digit, return the number alon represents.
8 
9 ;x10add : number number -> number
10 ;Given n1 and n2, multiply n2 by 10 (ie, x10) then add to n1 (ie, add).
11 
12 (define (build-number alon)
13   (local ((define (x10add n1 n2)
14             (+ (* n2 10) n1)))
15     (foldl x10add 0 alon)))
16 
17 ;;View
18 
19 (define a-msg (make-message "Please choose 3 digits"))
20 
21 ;;DIGITS is a list of gui-items [choice]
22 (define DIGITS (local ((define (create-choice-gui colnum)
23                          (make-choice (build-list 10 number->string))))
24                  (build-list 3 create-choice-gui)))
25 
26 ;;list-of-digit-choices : number -> gui-item [choice]
27 
28 
29 ;;Controller
30 
31 (define (submit-digits event)
32   (draw-message a-msg (number->string (build-number (map choice-index DIGITS)))))
33 
34 (create-window (list DIGITS
35                      (list a-msg)
36                      (list (make-button "Submit digits" submit-digits))))