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-advanced-reader.ss" "lang")((modname |29.3|) (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 #t #t none #f ((lib "draw.ss" "teachpack" "htdp") (lib "arrow.ss" "teachpack" "htdp") (lib "gui.ss" "teachpack" "htdp")))))
4 (define (find-route1 ori dest G)
5   (local ((define (find-route ori dest G)
6             (cond
7               [(symbol=? ori dest) (list ori)]
8               [else (local ((define possible-route (find-route/list (neighbors ori G) dest G)))
9                       (cond
10                         [(boolean? possible-route) false]
11                         [else (cons ori possible-route)]))]))
12           (define (find-route/list lo-ori dest G)
13             (cond
14               [(empty? lo-ori) false]
15               [else (local ((define possible-route (find-route (first lo-ori) dest G)))
16                       (cond [(boolean? possible-route) (find-route/list (rest lo-ori) dest G)]
17                             [else possible-route]))]))
18           (define (neighbors anode G)
19             (first (rest (assf (lambda (x) (equal? anode x)) G)))))
20     find-route ori dest G))
21 
22 (define (neighbors anode agraph)
23   (vector-ref agraph anode)) 
24 
25 
26 (define G (vector '(1 4)
27                   '(4 5)
28                   '(3)
29                   empty
30                   '(2 5)
31                   '(3 6)
32                   empty))
33 
34 ;find-route : node node graph -> (listof nodes)
35 ;Find a route from ori to dest given G and return the route as a (listof nodes).
36 
37 (define (find-route ori dest G)
38   (cond
39     [(= ori dest) (list ori)]
40     [else (local ((define possible-route (find-route/list (neighbors ori G) dest G)))
41             (cond [(boolean? possible-route) false]
42                   [else (cons ori possible-route)]))]))
43 
44 ;find-route/list : (listof nodes) node graph -> (listof nodes)
45 ;Find a route from lo-ori (listof nodes) to dest given G and return the route as a (listof nodes).
46 
47 (define (find-route/list lo-ori dest G)
48   (cond
49     [(empty? lo-ori) false]
50     [else (local ((define possible-route (find-route (first lo-ori) dest G)))
51             (cond
52               [(boolean? possible-route) (find-route/list (rest lo-ori) dest G)]
53               [else possible-route]))]))