From 85eb92df39b3825183d9a737aed0fdb3872c9241 Mon Sep 17 00:00:00 2001
From: Matthias Andreas Benkard <matthias@benkard.de>
Date: Mon, 23 Jun 2008 20:29:43 +0200
Subject: Allow binding NIL in environments.

---
 MLKEnvironment.m | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

(limited to 'MLKEnvironment.m')

diff --git a/MLKEnvironment.m b/MLKEnvironment.m
index 2dab2aa..581c462 100644
--- a/MLKEnvironment.m
+++ b/MLKEnvironment.m
@@ -74,7 +74,9 @@ static id UNBOUND;
 
 -(void) setValue:(id)value forBinding:(MLKSymbol *)symbol;
 {
-  [self setBinding:symbol to:value inEnvironment:self];
+  [self setBinding:(symbol ? (id)symbol : (id)[NSNull null])
+        to:value
+        inEnvironment:self];
 }
 
 -(void) setBinding:(MLKSymbol *)symbol to:(id)value inEnvironment:(MLKEnvironment *)env
@@ -93,7 +95,8 @@ static id UNBOUND;
 
 -(id) valueForBinding:(MLKSymbol *)symbol
 {
-  return [self valueForBinding:symbol inEnvironment:self];
+  return [self valueForBinding:(symbol ? (id)symbol : (id)[NSNull null])
+               inEnvironment:self];
 }
 
 -(id) valueForBinding:(MLKSymbol *)symbol inEnvironment:(MLKEnvironment *)env
@@ -134,7 +137,7 @@ static id UNBOUND;
 
 -(void) addBinding:(MLKSymbol *)symbol
 {
-  [_bindings setObject:UNBOUND forKey:symbol];
+  [_bindings setObject:UNBOUND forKey:(symbol ? (id)symbol : (id)[NSNull null])];
 }
 
 -(MLKEnvironment *) environmentForBinding:(MLKSymbol *)symbol
-- 
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