# HG changeset patch
# User Stefan Vogel <sv@exept.de>
# Date 1467217672 -7200
# Node ID cbe2e415bb782547114f69d14b172a0792b85bb8
# Parent  cafe55f1d865290e2b919cf9d4706e8cb8a4a4e9
#FEATURE by stefan
class: LazyValue
class definition
added: #displayOn:
removed:
        #initialize
        #printOn:
changed:
        #_evaluate_
        #block:
        #displayString
category of: #isLazyValue
    do not use a global lock, use per instance Semaphore instead

diff -r cafe55f1d865 -r cbe2e415bb78 LazyValue.st
--- a/LazyValue.st	Mon Jun 27 17:26:27 2016 +0200
+++ b/LazyValue.st	Wed Jun 29 18:27:52 2016 +0200
@@ -9,12 +9,13 @@
  other person.  No title to or ownership of the software is
  hereby transferred.
 "
-
 "{ Package: 'stx:libbasic2' }"
 
+"{ NameSpace: Smalltalk }"
+
 ProtoObject subclass:#LazyValue
-	instanceVariableNames:'result block'
-	classVariableNames:'AccessLock'
+	instanceVariableNames:'result block lock'
+	classVariableNames:''
 	poolDictionaries:''
 	category:'Kernel-Processes'
 !
@@ -395,12 +396,6 @@
 "
 ! !
 
-!LazyValue class methodsFor:'initialization'!
-
-initialize
-    AccessLock := RecursionLock forMutualExclusion
-! !
-
 !LazyValue class methodsFor:'instance creation'!
 
 block:aBlock
@@ -420,13 +415,13 @@
 
 _evaluate_
     block notNil ifTrue:[
-        AccessLock critical:[
-            |b|
+        lock wait.   "ensure that block is only executed once"
+        block notNil ifTrue:[
+            result := block value.
+            block := nil.
 
-            (b := block) notNil ifTrue:[
-                block := nil.
-                result := b value.
-            ].
+            lock signalForAll.
+            lock := nil.
         ].
     ].
     ^ result
@@ -434,43 +429,59 @@
 
 !LazyValue methodsFor:'printing'!
 
-displayString
+displayOn:aGCOrStream
+
+    "/ what a kludge - Dolphin and Squeak mean: printOn: a stream;
+    "/ ST/X (and some old ST80's) mean: draw-yourself on a GC.
+    (aGCOrStream isStream) ifFalse:[
+        ^ self _evaluate_ displayOn:aGCOrStream
+    ].
+
     block isNil ifTrue:[
-        ^ 'LazyValue (unevaluated)'
-    ].
-    ^ 'LazyValue (evaluated)'
+        result displayOn:aGCOrStream.
+        aGCOrStream nextPutAll:' (lazyValue evaluated)'.
+        ^ self.
+    ].    
+    aGCOrStream nextPutAll:'LazyValue (unevaluated)'
 !
 
-printOn:aStream
-    aStream nextPutAll:'(lazy)'
+displayString
+    |s|
+
+    "/ attention: TextStream is not present in ultra-mini standalone apps
+    s := TextStream isNil
+            ifTrue:['' writeStream]
+            ifFalse:[TextStream on:(String new:32)].
+    self displayOn:s.
+    ^ s contents
 ! !
 
 !LazyValue methodsFor:'private access'!
 
 block:aBlock
     block := aBlock.
+    lock := Semaphore forMutualExclusion.
 ! !
 
 !LazyValue methodsFor:'queries'!
 
 class
     ^ self _evaluate_ class
+! !
+
+!LazyValue methodsFor:'testing'!
+
+isBehavior
+    ^ self _evaluate_ isBehavior
 !
 
 isLazyValue
     ^ block notNil
 ! !
 
-!LazyValue methodsFor:'testing'!
-
-isBehavior
-    ^ self _evaluate_ isBehavior
-! !
-
 !LazyValue class methodsFor:'documentation'!
 
 version
-    ^ '$Header: /cvs/stx/stx/libbasic2/LazyValue.st,v 1.5 2005-01-26 13:54:57 stefan Exp $'
+    ^ '$Header$'
 ! !
 
-LazyValue initialize!