Class: False

• Inheritance
• Description
• Related information
• Instance protocol
  • binary storage
  • conditional evaluation
  • converting
  • logical operations
  • printing & storing

Inheritance:

   Object
   |
   +--Boolean
      |
      +--False

Package:

stx:libbasic

Category:

Kernel-Objects

Version:

rev: 1.28 date: 2009/09/14 12:49:49

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 thruth 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:

 storeBinaryOn: stream manager: manager

store a binary representation of the receiver on stream;
redefined, since false is stored with a special type-code

 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.

 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.

 and: block1 and: block2 and: block3

return false

 and: block1 and: block2 and: block3 and: block4

return false

 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 blocks value.
Notice:
This method is open coded (inlined) by the compiler(s)
- redefining it may not work as expected.

 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.

 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.

 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.

 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.

 or: block1 or: block2

 or: block1 or: block2 or: block3

 or: block1 or: block2 or: block3 or: block4

 asInteger

false->0; true->1

 asNumber

false->0; true->1

 & 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.

 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)

 implies: aBoolean

return true if receiver => argument

 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.

 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)

 | 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.

 printString

return character sequence representing the receiver