--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/BooleanValueHolder.st	Sat May 17 12:18:52 2008 +0200
@@ -0,0 +1,141 @@
+"
+ COPYRIGHT (c) 2008 by Claus Gittinger
+              All Rights Reserved
+
+ This software is furnished under a license and may be used
+ only in accordance with the terms of that license and with the
+ inclusion of the above copyright notice.   This software may not
+ be provided or otherwise made available to, or used by, any
+ other person.  No title to or ownership of the software is
+ hereby transferred.
+"
+"{ Package: 'stx:libview2' }"
+
+ValueHolder subclass:#BooleanValueHolder
+	instanceVariableNames:''
+	classVariableNames:''
+	poolDictionaries:''
+	category:'Interface-Support-Models'
+!
+
+!BooleanValueHolder class methodsFor:'documentation'!
+
+copyright
+"
+ COPYRIGHT (c) 2008 by Claus Gittinger
+              All Rights Reserved
+
+ This software is furnished under a license and may be used
+ only in accordance with the terms of that license and with the
+ inclusion of the above copyright notice.   This software may not
+ be provided or otherwise made available to, or used by, any
+ other person.  No title to or ownership of the software is
+ hereby transferred.
+"
+!
+
+documentation
+"
+    a valueHolder holding a boolean.
+    Mostly for documentation purposes and the assertion, that only boolean values
+    are held. Also provides convenient logical operations.
+
+    [author:]
+        Claus Gittinger
+"
+!
+
+examples 
+"
+                                                                        [exBegin]
+     |b nb|
+
+     b := BooleanValueHolder new.
+     nb := b not.
+     b value:true.
+     nb value.     
+     b value:false.
+     nb value.     
+                                                                        [exEnd]
+"
+! !
+
+!BooleanValueHolder class methodsFor:'instance creation'!
+
+new
+    "return a new BooleanValueHolder holding false as initial value"
+
+    ^ self with:false
+! !
+
+!BooleanValueHolder methodsFor:'accessing'!
+
+setValue:aBoolean
+    self assert:aBoolean isBoolean.
+    value := aBoolean.
+! !
+
+!BooleanValueHolder methodsFor:'logical operations'!
+
+& anotherBooleanValueHolder
+    "return another valueHolder, which returns the logical and of myself and another valueHolder"
+
+    ^ BlockValue 
+        forLogical:self and:anotherBooleanValueHolder
+
+    "
+     |b1 b2 a|
+
+     b1 := BooleanValueHolder new.
+     b2 := BooleanValueHolder new.
+     a := b1 & b2.
+     b1 value:false.
+     b2 value:true.
+     a value.      
+     b1 value:true.
+     a value.     
+    "
+!
+
+not
+    "return another valueHolder, which returns the logical not of myself"
+
+    ^ BlockValue forLogicalNot:self.
+
+    "
+     |b nb|
+
+     b := BooleanValueHolder new.
+     nb := b not.
+     b value:true.
+     nb value.     
+     b value:false.
+     nb value.     
+    "
+!
+
+| anotherBooleanValueHolder
+    "return another valueHolder, which returns the logical and of myself and another valueHolder"
+
+    ^ BlockValue 
+        forLogical:self or:anotherBooleanValueHolder
+
+    "
+     |b1 b2 o|
+
+     b1 := BooleanValueHolder new.
+     b2 := BooleanValueHolder new.
+     o := b1 | b2.
+     b1 value:false.
+     b2 value:false.
+     o value.      
+     b1 value:true.
+     o value.     
+    "
+! !
+
+!BooleanValueHolder class methodsFor:'documentation'!
+
+version
+    ^ '$Header: /cvs/stx/stx/libview2/BooleanValueHolder.st,v 1.1 2008-05-17 10:18:52 cg Exp $'
+! !