Add amb and distinct?

test.scm

@@ -80,3 +80,22 @@
     (assert-equal 2 (number-generator))
     (assert-equal 3 (number-generator))
     (assert-equal 4 (number-generator))))
+
+(define-test-suite "amb"
+  (define-test "liars"
+    (define (liars)
+      (amb-reset)
+      (let ([betty (amb 1 2 3 4 5)]
+	    [ethel (amb 1 2 3 4 5)]
+	    [joan  (amb 1 2 3 4 5)]
+	    [kitty (amb 1 2 3 4 5)]
+	    [mary  (amb 1 2 3 4 5)])
+	;; The "Liars" problem
+	(amb-require (distinct? betty ethel joan kitty mary))
+	(amb-require (or (= kitty 1) (= betty 3)))
+	(amb-require (or (= ethel 1) (= joan  2)))
+	(amb-require (or (= joan  3) (= ethel 5)))
+	(amb-require (or (= kitty 2) (= mary  4)))
+	(amb-require (or (= mary  4) (= betty 1)))
+	(list betty ethel joan kitty mary)))
+    (assert-equal '(3 5 2 1 4) (liars))))