new tasks

Task/Assertions/Racket/assertions-2.rkt

@@ -0,0 +1,5 @@
+#lang racket
+
+(define x 80)
+(unless (= x 42)
+  (error "a is not 42")) ; will error

Task/Assertions/Racket/assertions.rkt

@@ -0,0 +1,13 @@
+#lang racket
+
+(define/contract x
+  (=/c 42) ; make sure x = 42
+  42)
+
+(define/contract f
+  (-> number? (or/c 'yes 'no)) ; function contract
+  (lambda (x)
+    (if (= 42 x) 'yes 'no)))
+
+(f 42)    ; succeeds
+(f "foo") ; contract error!