cities path

clitests/cities.psil

@@ -0,0 +1,90 @@
+(define (equal? a b)
+  (if (nil? a) (if (nil? b) 1 0)
+    (if (atom a)
+      (if (atom b) (= a b) 0)
+      (if (atom b) 0 (if (equal? (car a) (car b)) (equal? (cdr a) (cdr b)) 0))
+    )
+  )
+)
+
+(define (empty? l)
+    (equal? l (nil))
+)
+
+(define (not a)
+    (if a 0 1)
+)
+
+(not 2)
+(not 1)
+(not 0)
+
+
+(define (lhas list what)
+  (if (empty? list) 0
+  (if (equal? (car list) what) 1 (lhas (cdr list) what))
+)
+)
+
+(define (onehas list l)
+  (if (empty? list) 0
+  (if (l (car list)) 1 (onehas (cdr list) l))
+)
+)
+
+(define (appfront list what)
+(cons what list)
+  )
+
+(define (pathslist acc paths from)
+  (if (empty? paths)
+      acc
+      (if (equal? (car (car paths)) from)
+          (pathslist (appfront acc (car(cdr (car paths)))) (cdr paths) from)
+          (pathslist acc (cdr paths) from)
+          )
+  )
+)
+
+(equal? (pathslist () (quote((1 2))) 1) (quote(2)))
+
+
+(define (filter p l)
+(if (empty? l) (nil)
+    (if (p (car l))
+        (cons (car l) (filter p (cdr l)) )
+        (filter p (cdr l))
+        )
+))
+
+(filter (lambda (x) (if (> x 0) 1 0 )) (quote(-1 2 0 3 -3 1)))
+(equal? (filter (lambda (x) (if (> (car x) 0) (if (> (car(cdr x)) 0) 1 0) 0 )) (quote((-1 2) (0 3) (-3 1) (1 1)))) (quote((1 1))))
+
+(define (cities-path-impl seen paths from to)
+  (if (equal? from to)
+      1
+      (onehas
+             (filter (lambda (w) (not (lhas (appfront seen from) w))) (pathslist (nil) paths from))
+             (lambda (f) (cities-path-impl (appfront seen from) paths f to))
+       )
+      )
+  )
+
+(define (cities-path? paths from to)
+  (cities-path-impl (nil) paths from to)
+)
+
+(cities-path? (nil) 1 2)
+(cities-path? (nil) 2 2)
+(cities-path? (quote((1 2))) 1 2)
+(cities-path? (quote((1 2))) 1 3)
+(cities-path? (quote((1 2))) 2 1)
+(cities-path? (quote((2 1))) 1 2)
+(cities-path? (quote((1 2) (2 1))) 1 2)
+(cities-path? (quote((1 2) (2 1))) 2 1)
+(cities-path? (quote((1 2) (2 3) (3 4) (4 2))) 1 2)
+(cities-path? (quote((1 2) (2 3) (3 4) (4 2))) 1 3)
+(cities-path? (quote((1 2) (2 3) (3 4) (4 2))) 1 4)
+(cities-path? (quote((1 2) (2 3) (3 4) (4 2))) 2 3)
+(cities-path? (quote((1 2) (2 3) (3 4) (4 2))) 2 4)
+(cities-path? (quote((4 2) (3 4) (2 3) (1 2))) 3 2)

clitests/cities.psil.ex

@@ -0,0 +1,20 @@
+0
+0
+1
+1
+(2 3 1)
+1
+0
+1
+1
+0
+0
+0
+1
+1
+1
+1
+1
+1
+1
+1