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Documentation of class 'False':

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Class: False


Inheritance:

   Object
   |
   +--Boolean
      |
      +--False

Package:
stx:libbasic
Category:
Kernel-Objects
Version:
rev: 1.34 date: 2019/03/13 09:31:40
user: cg
file: False.st directory: libbasic
module: stx stc-classLibrary: libbasic
Author:
Claus Gittinger

Description:


False has only one instance, false, representing logical falsehood.

Some methods are implemented here and in True, instead of the common
superclass Boolean. This has the advantage that no truth-value checks
are needed, but instead the truth check is done in the method lookup.
However, remember that some messages to booleans are inline coded in
the compilers (both interpreted and machine code). Therefore redefinition
of some methods here will not have any effect on compiled code.
(redefining ifTrue: to something else will probably crash the smalltalk
 world anyway ...)


Related information:

    True

Instance protocol:

Javascript support
o  js_not
( an extension from the stx:libjavascript package )

conditional evaluation
o  and: aBlock
evaluate aBlock if the receiver is true.
(since the receiver is known to be false here, always return false here).
Notice:
This method is open coded (inlined) by the compiler(s)
- redefining it may not work as expected.

o  and: block1 and: block2
evaluate block1 if the receiver is true; if that also returns true, evaluate block2.
(since the receiver is known to be false here, always return false here).
Notice:
This method is open coded (inlined) by the compiler(s)
- redefining it may not work as expected.

o  and: block1 and: block2 and: block3
evaluate block1 if the receiver is true;
if that also returns true, evaluate block2;
if that also returns true, evaluate block3.
(since the receiver is known to be false here, always return false here).
Notice:
This method may be open coded (inlined) by the compiler(s)
- redefining it may not work as expected.

o  and: block1 and: block2 and: block3 and: block4
evaluate block1 if the receiver is true;
if that also returns true, evaluate block2;
if that also returns true, evaluate block3.
if that also returns true, evaluate block4.
(since the receiver is known to be false here, always return false here).
Notice:
This method may be open coded (inlined) by the compiler(s)
- redefining it may not work as expected.

o  ifFalse: aBlock
If the receiver is false, return the value of evaluating aBlock; nil otherwise.
Since the receiver is definitely false here, unconditionally return the block's value.
Notice:
This method is open coded (inlined) by the compiler(s)
- redefining it may not work as expected.

o  ifFalse: falseBlock ifTrue: trueBlock
return the value of evaluating falseBlock (since the receiver is false)
Notice:
This method is open coded (inlined) by the compiler(s)
- redefining it may not work as expected.

o  ifTrue: aBlock
If the receiver is true, return the value of evaluating aBlock; nil otherwise.
Since the receiver is definitely false here, unconditionally return nil value.
Notice:
This method is open coded (inlined) by the compiler(s)
- redefining it may not work as expected.

o  ifTrue: trueBlock ifFalse: falseBlock
return the value of evaluating falseBlock (since the receiver is false)
Notice:
This method is open coded (inlined) by the compiler(s)
- redefining it may not work as expected.

o  or: aBlock
evaluate aBlock if the receiver is false.
(since the receiver is false return the value of evaluating aBlock).
Notice:
This method is open coded (inlined) by the compiler(s)
- redefining it may not work as expected.

o  or: block1 or: block2
evaluate block1 if the receiver is false.
if that evaluates to false, return the result from block2.
(since the receiver is false return the value of evaluating aBlock).
Notice:
This method may be open coded (inlined) by the compiler(s)
- redefining it may not work as expected.

o  or: block1 or: block2 or: block3
evaluate block1 if the receiver is false.
if that evaluates to false, return the result from block2.
if that evaluates to false, return the result from block3.
(since the receiver is false return the value of evaluating aBlock).
Notice:
This method may be open coded (inlined) by the compiler(s)
- redefining it may not work as expected.

o  or: block1 or: block2 or: block3 or: block4
evaluate block1 if the receiver is false.
if that evaluates to false, return the result from block2.
if that evaluates to false, return the result from block3.
if that evaluates to false, return the result from block4.
(since the receiver is false return the value of evaluating aBlock).
Notice:
This method may be open coded (inlined) by the compiler(s)
- redefining it may not work as expected.

converting
o  asInteger
false->0; true->1

o  asNumber
false->0; true->1

debugging
o  haltIfFalse
halt if the receiver is true

usage example(s):

     3 haltIfNil
     nil haltIfNil

     true haltIfTrue
     true haltIfFalse

     false haltIfTrue
     false haltIfFalse

o  haltIfTrue
halt if the receiver is true

inspecting
o  inspectorValueListIconFor: anInspector
( an extension from the stx:libtool package )
returns the icon to be shown alongside the value list of an inspector

logical operations
o  & aBoolean
return true, if both the receiver and the argument are true
(since the receiver is false, return false)
Notice:
as this is a binary message, the argument is always evaluated.
It might be better to use and:[...], which does not evaluate
the argument if the receiver is already false.

o  ==> aBoolean
same as implies:
return true if receiver => argument

o  eqv: aBoolean
return true, if the receiver and the argument are the same truth value
(since the receiver is false, return true if the argument is also false)

o  implies: aBoolean
return true if receiver => argument

o  not
return true, if the receiver is false, false otherwise
(since the receiver is false, return true).
Notice:
This method is open coded (inlined) by the compiler(s)
- redefining it may not work as expected.

o  xor: aBoolean
return true, if the receiver and the argument are different truth values
(since the receiver is false, return true, if the armument is not false)

o  | aBoolean
return true, if either the receiver or the argument is true
(since the receiver is false, return the argument).
Notice:
as this is a binary message, the argument is always evaluated.
It might be better to use or:[...], which does not evaluate
the argument if the receiver is already true.

printing & storing
o  printString
return character sequence representing the receiver



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