From f373e5ae76b025dc5ed5ec47bf37565b2c3188a2 Mon Sep 17 00:00:00 2001
From: Jan Nieuwenhuizen <janneke@gnu.org>
Date: Sun, 10 Jul 2016 13:04:10 +0200
Subject: [PATCH] add not, if.

---
 scm.mes  | 11 +++++++++++
 test.mes |  7 +++++++
 2 files changed, 18 insertions(+)

diff --git a/scm.mes b/scm.mes
index e13eedc7..e9ddef52 100755
--- a/scm.mes
+++ b/scm.mes
@@ -64,3 +64,14 @@
         ((null? r) (cons (f (car l)) (map f (cdr l))))
         ((null? (cdr r))
          (cons (f (car l) (caar r)) (map f (cdr l) (cdar r))))))
+
+(define (not x)
+  (cond (x #f)
+        (#t #t)))
+
+(define-macro (if expr then . else)
+  (cond ((not (eq? (c:eval expr (current-module)) #f))
+         then)
+        (#t
+         (cond ((pair? else) (car else))
+               (#t *unspecified*)))))
diff --git a/test.mes b/test.mes
index 619f25a0..96a0fe23 100644
--- a/test.mes
+++ b/test.mes
@@ -124,4 +124,11 @@
 (display (= 3 '3))
 (newline)
 
+(display (if #t 'true))
+(newline)
+(display (if (eq? 0 '0) 'true 'false))
+(newline)
+(display (if (= 1 2) 'true 'false))
+(newline)
+
 '()