moar

seasoning.rkt

@@ -50,9 +50,9 @@
   (cond
     ((null? lat) #f)
     (else
-    (or
-     (two-in-a-row-b? (car lat) (cdr lat))
-     (eq? preceeding (car lat))))))
+     (or
+      (eq? preceeding (car lat))
+      (two-in-a-row-b? (car lat) (cdr lat))))))
 
 (define (two-in-a-row-final? lat)
   (cond
@@ -66,3 +66,55 @@
 (check-equal?
  (two-in-a-row-final? '(italian sardines sardines spaghetti parsley))
  #t)
+(check-equal?
+ (two-in-a-row-final? '(d e i i a g))
+ #t)
+
+(define (sum-of-prefixes lat)
+  (cond
+    ((null? lat) '())
+    (else
+     (sum-of-prefixes-b 0 lat))))
+
+(define (sum-of-prefixes-b sumsofar tup)
+  (cond
+    ((null? tup) '())
+    (else
+     (cons
+      (+ sumsofar (car tup))
+      (sum-of-prefixes-b
+       (+ sumsofar (car tup))
+       (cdr tup))))))
+
+(check-equal?
+ (sum-of-prefixes '(2 1 9 17 0))
+ '(2 3 12 29 29))
+(check-equal?
+ (sum-of-prefixes '(1 1 1 1 1))
+ '(1 2 3 4 5))
+
+(define (pick n lat)
+  (cond
+    ((eq? n 1) (car lat))
+    (else (pick (sub1 n) (cdr lat)))))
+
+(check-equal? (pick 1 '(1 2 3 4 5)) 1)
+(check-equal? (pick 3 '(1 2 3 4 5)) 3)
+(check-equal? (pick 5 '(1 2 3 4 5)) 5)
+
+(define (scramble tup)
+  (cond
+    ((null? tup) '())
+    (else (scramble-b tup '()))))
+
+(define (scramble-b tup reversed-prefix)
+  (cond
+    ((null? tup) '())
+    (else
+     (cons
+      (pick (car tup) (cons (car tup) reversed-prefix))
+      (scramble-b (cdr tup) (cons (car tup) reversed-prefix))))))
+
+(check-equal? (scramble '(1 1 1 3 4 2 1 1 9 2)) '(1 1 1 1 1 4 1 1 1 9))
+(check-equal? (scramble '(1 2 3 4 5 6 7 8 9)) '(1 1 1 1 1 1 1 1 1))
+(check-equal? (scramble '(1 2 3 1 2 3 4 1 8 2 10)) '(1 1 1 1 1 1 1 1 2 8 2))