list contains implemented

snippets/userlib-tests.rls

@@ -55,6 +55,18 @@
              (adder (lambda (x y) (add x y))))
          (eq? (reduce adder list) (add 1 2 3)))))
 
+   ('contains? finds elem in list'
+     (quote
+       (contains? (1 2 3) 1)))
+
+   ('contains? finds last elem in list'
+     (quote
+       (contains? (1 2 3) 3)))
+
+   ('contains? doesnt find elem not in list'
+     (quote
+       (not (contains? (1 2 3) 4))))
+
      ;; add more test cases here
    ))
 

snippets/userlib.rls

@@ -85,3 +85,18 @@ this will continue iuntil the list is exhausted.'
           (set (q result) (func result current))
           (set (q list-iter) (pop remaining)))))
   result))
+
+(def contains?
+'Takes two arguments: a list and an element.
+Returns true if the list contains the element.'
+(list elem)
+(let ((found false)
+      (list-iter (pop list)))
+  (while (and (gt? (len list-iter) 1)
+              (not found))
+    (let ((current (car list-iter))
+          (remaining (cdr list-iter)))
+      (if (eq? current elem)
+        (set (q found) true)
+        (set (q list-iter) (pop remaining)))))
+  found))