From d34366c38b2828bbeb0a417850a22bd0e2bf18e5 Mon Sep 17 00:00:00 2001
From: Chris Hanson <org/chris-hanson/cph>
Date: Fri, 26 Feb 2016 08:30:57 +0000
Subject: [PATCH] Implement when and unless from r7rs.

---
 src/runtime/mit-macros.scm | 14 +++++++++++++-
 src/runtime/runtime.pkg    |  4 +++-
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/src/runtime/mit-macros.scm b/src/runtime/mit-macros.scm
index 43e17efcf..76df49bf0 100644
--- a/src/runtime/mit-macros.scm
+++ b/src/runtime/mit-macros.scm
@@ -736,4 +736,16 @@ USA.
   (syntax-rules ()
     ((ASSERT condition . extra)
      (IF (NOT condition)
-         (ERROR "Assertion failed:" 'condition . extra)))))
\ No newline at end of file
+         (ERROR "Assertion failed:" 'condition . extra)))))
+
+(define-syntax :when
+  (syntax-rules ()
+    ((when condition form ...)
+     (if condition
+	 (begin form ...)))))
+
+(define-syntax :unless
+  (syntax-rules ()
+    ((unless condition form ...)
+     (if (not condition)
+	 (begin form ...)))))
\ No newline at end of file
diff --git a/src/runtime/runtime.pkg b/src/runtime/runtime.pkg
index ac828021a..f59e2fcfd 100644
--- a/src/runtime/runtime.pkg
+++ b/src/runtime/runtime.pkg
@@ -4907,7 +4907,9 @@ USA.
 	  (local-declare :local-declare)
 	  (parameterize :parameterize)
 	  (quasiquote :quasiquote)
-	  (receive :receive))
+	  (receive :receive)
+	  (unless :unless)
+	  (when :when))
   (export (runtime)
 	  parse-define-form))
 
-- 
2.25.1