start seasoned schemer

seasoning.rkt

@@ -0,0 +1,68 @@
+#lang racket
+(require rackunit)
+
+(define (atom? x)
+  (and
+   (not (pair? x))
+   (not (null? x))))
+
+(check-equal? (atom? '()) #f)
+
+(define (add1 n)
+  (+ n 1))
+
+(define (sub1 n)
+  (- n 1))
+
+(define (member? a lat)
+  (cond
+    ((null? lat) #f)
+    (else (or
+           (eq? a (car lat))
+           (member? a (cdr lat))))))
+
+(check-equal?
+ (member? 'sardines '(italian sardines spaghetti parsley))
+ #t)
+
+(define (two-in-a-row? lat)
+  (cond
+    ((null? lat) #f)
+    (else
+     (is-first-b? (car lat) (cdr lat)))))
+
+(define (is-first-b? a lat)
+  (cond
+    ((null? lat) #f)    
+    (else
+     (or
+      (eq? a (car lat))
+      (two-in-a-row? lat)))))
+
+(check-equal?
+ (two-in-a-row? '(italian sardines spaghetti parsley))
+ #f)
+(check-equal?
+ (two-in-a-row? '(italian sardines sardines spaghetti parsley))
+ #t)
+
+(define (two-in-a-row-b? preceeding lat)
+  (cond
+    ((null? lat) #f)
+    (else
+    (or
+     (two-in-a-row-b? (car lat) (cdr lat))
+     (eq? preceeding (car lat))))))
+
+(define (two-in-a-row-final? lat)
+  (cond
+    ((null? lat) #f)
+    (else
+     (two-in-a-row-b? (car lat) (cdr lat)))))
+
+(check-equal?
+ (two-in-a-row-final? '(italian sardines spaghetti parsley))
+ #f)
+(check-equal?
+ (two-in-a-row-final? '(italian sardines sardines spaghetti parsley))
+ #t)