Class: Boolean

• Inheritance
• Description
• Class protocol
  • instance creation
  • queries
• Instance protocol
  • Javascript support
  • blocked
  • converting
  • copying
  • inspecting
  • printing & storing
  • testing
  • tracing
  • visiting

Inheritance:

   Object
   |
   +--Boolean
      |
      +--False
      |
      +--True

Package:

stx:libbasic

Category:

Kernel-Objects

Version:

rev: 1.44 date: 2015/11/18 12:17:52

user: cg

file: Boolean.st directory: libbasic

module: stx stc-classLibrary: libbasic

Author:

Claus Gittinger

Description:

Boolean is an abstract class defining the common protocol for logical
values. The logical values are represented by its two subclasses True and False.

There are no instances of Boolean in the system and there is only one
instance of True (which is the global true) and one of False (false).

Boolean redefines some messages which deal with copying Booleans,
to make certain there is only one instance of each.
The system will behave strange if you fiddle around here and create
new instances of True or False (i.e. it will not recognize these new
instances as being true or false).

Class protocol:

 basicNew

catch instance creation
- there must be exactly one instance of each - no more

 readFrom: aStringOrStream onError: exceptionBlock

return a new Boolean, reading a printed representation from aStringOrStream.

usage example(s):

Boolean readFrom:'true' Boolean readFrom:'false' Boolean readFrom:'xxx' Boolean readFrom:' true' Boolean readFrom:' false' Boolean readFrom:'true xxx' Boolean readFrom:'false xxx' Boolean readFromString:'true xxx' Boolean readFromString:'false xxx'

 hasSharedInstances

return true if this class has shared instances, that is, instances
with the same value are identical.
True returned here - there is only one true and only one false.

 isAbstract

 isBuiltInClass

return true if this class is known by the run-time-system.
Here, true is returned (for my two subclasses).

Instance protocol:

 js_asBoolean
( an extension from the stx:libjavascript package )

 typeof
( an extension from the stx:libjavascript package )

return a string describing what I am

usage example(s):

JavaScriptParser evaluate:'''hello''.typeof()' JavaScriptParser evaluate:'false.typeof();'

 addDependent: someOne

not really an error ...

 onChangeSend: selector to: someOne

not really an error ...

 asBoolean

 literalArrayEncoding

encode myself as an array literal, from which a copy of the receiver
can be reconstructed with #decodeAsLiteralArray.

 copy

return a shallow copy of the receiver
- since both true and false are unique, return the receiver

 deepCopyUsing: aDictionary postCopySelector: postCopySelector

return a deep copy of the receiver
- since both true and false are unique, return the receiver

 shallowCopy

return a shallow copy of the receiver
- since both true and false are unique, return the receiver

 simpleDeepCopy

return a deep copy of the receiver
- since both true and false are unique, return the receiver

 inspectorValueStringInListFor: anInspector
( an extension from the stx:libtool package )

returns a string to be shown in the inspector's selection list

 printOn: aStream

append a character sequence representing the receiver to the argument, aStream

 storeOn: aStream

append a character sequence to the argument, aStream from which the
receiver can be reconstructed using readFrom:.

 storeString

return a character sequence to the argument, aStream from which the
receiver can be reconstructed using readFrom:.

 isBoolean

Return true, because it is a boolean.

 isLiteral

return true, if the receiver can be used as a literal constant in ST syntax
(i.e. can be used in constant arrays)

 traceInto: aRequestor level: level from: referrer

double dispatch into tracer, passing my type implicitely in the selector

 acceptVisitor: aVisitor with: aParameter

dispatch for visitor pattern; send #visitBoolean:with: to aVisitor