pulled in lisp koans for solving

https://github.com/google/lisp-koans

lisp-koans/koans-solved/control-statements.lisp

@@ -0,0 +1,68 @@
+;;; Copyright 2013 Google Inc.
+;;;
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
+;;;
+;;;     http://www.apache.org/licenses/LICENSE-2.0
+;;;
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
+
+(define-test if
+  ;; IF only evaluates and returns one branch of a conditional expression.
+  (assert-equal :true (if t :true :false))
+  (assert-equal :false (if nil :true :false))
+  ;; This also applies to side effects that migh or might not be evaluated.
+  (let ((result))
+    (if t
+        (setf result :true)
+        (setf result :false))
+    (assert-equal :true result)
+    (if nil
+        (setf result :true)
+        (setf result :false))
+    (assert-equal :false result)))
+
+(define-test when-unless
+  ;; WHEN and UNLESS are like one-branched IF statements.
+  (let ((when-result nil)
+        (when-numbers '())
+        (unless-result nil)
+        (unless-numbers '()))
+    (dolist (x '(1 2 3 4 5 6 7 8 9 10))
+      (when (> x 5)
+        (setf when-result x)
+        (push x when-numbers))
+      (unless (> x 5)
+        (setf unless-result x)
+        (push x unless-numbers)))
+    (assert-equal 10 when-result)
+    (assert-equal '(10 9 8 7 6) when-numbers)
+    (assert-equal 5 unless-result)
+    (assert-equal '(5 4 3 2 1) unless-numbers)))
+
+(define-test and-short-circuit
+  ;; AND only evaluates forms until one evaluates to NIL.
+  (assert-equal 5
+                (let ((x 0))
+                  (and
+                   (setf x (+ 2 x))
+                   (setf x (+ 3 x))
+                   nil
+                   (setf x (+ 4 x)))
+                  x)))
+
+(define-test or-short-circuit
+  ;; OR only evaluates forms until one evaluates to non-NIL.
+  (assert-equal 2
+                (let ((x 0))
+                  (or
+                   (setf x (+ 2 x))
+                   (setf x (+ 3 x))
+                   nil
+                   (setf x (+ 4 x)))
+                  x)))