Feat: if-not, if-not-let

If-not-let code, documentation, tests adapted from alexandria.

binding.lisp

@@ -324,3 +324,41 @@ Also, this version makes the bindings immutable."
                                           `(function ,(car binding)))
                                         bindings)))
      ,@body))
+
+(defmacro if-not (test then &optional else)
+  "If TEST evaluates to NIL, evaluate THEN and return its values,
+otherwise evaluate ELSE and return its values. ELSE defaults to NIL."
+  `(if (not ,test)
+       ,then
+       ,else))
+
+(defmacro if-not-let (bindings &body (then-form &optional else-form))
+  "Creates new variable bindings, and conditionally executes either
+THEN-FORM or ELSE-FORM. ELSE-FORM defaults to NIL.
+
+BINDINGS must be either single binding of the form:
+
+ (variable initial-form)
+
+or a list of bindings of the form:
+
+ ((variable-1 initial-form-1)
+  (variable-2 initial-form-2)
+  ...
+  (variable-n initial-form-n))
+
+All initial-forms are executed sequentially in the specified order. Then all
+the variables are bound to the corresponding values.
+
+If one of the variables was bound to NIL, the THEN-FORM is executed with the
+bindings in effect, otherwise the ELSE-FORM is executed with the bindings in
+effect.
+Adapted from Alexandria if-let."
+  (let* ((binding-list (if (and (consp bindings) (symbolp (car bindings)))
+                           (list bindings)
+                           bindings))
+         (variables (mapcar #'car binding-list)))
+    `(let ,binding-list
+       (if-not (and ,@variables)
+	       ,then-form
+	       ,else-form))))

package.lisp

@@ -193,6 +193,8 @@
    #:lret
    #:lret*
    #:and-let*
+   #:if-not
+   #:if-not-let
    #:recklessly-continue
    #:static-binding-flush-error
    #:static-binding-flush-error-group

tests/binding.lisp

@@ -167,3 +167,45 @@
     (eval `(and-let* ((x 1)
                       (y 2))
              x))))
+
+(test if-not
+  (is (= 2 (if-not t 1 2)))
+  (is (= 2 (if-not "test" 1 2)))
+  (is (= 1 (if-not nil 1 2)))
+  (is (null (if-not t 1))))
+
+;; tests adapted from Alexandria/tests
+(declaim (notinline opaque))
+(defun opaque (x)
+  x)
+
+(test if-not-let
+  (is (eql (if-not-let (x (opaque :ok))
+	     :bad
+	     x)
+	   :ok))
+  (is (eql :ok
+	   (if-not-let (x (opaque nil))
+	     (and (not x) :ok)
+	     :bad)))
+  (is (= 3
+	 (let ((x 1))
+	   (if-not-let ((x 2)
+			(y x))
+	     :oops
+	     (+ x y)))))
+  (is (= 1
+	 (if-not-let ((x 1)
+		      (y nil))
+           (and (not y) x)
+	   :oops)))
+  (is (if-not-let (x)
+	(not x)
+	:oops))
+  (is (eql :type-error
+	   (handler-case
+	       (eval '(if-not-let x
+		       :oops
+		       :oops))
+	     (type-error ()
+	       :type-error)))))