"

 COPYRIGHT (c) 1988 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.

"

String subclass:#Symbol

       instanceVariableNames:''

       classVariableNames:''

       poolDictionaries:''

       category:'Collections-Text'

!

Symbol comment:'

COPYRIGHT (c) 1988 by Claus Gittinger

	      All Rights Reserved

'!

!Symbol class methodsFor:'documentation'!

copyright

"

 COPYRIGHT (c) 1988 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.

"

!

version

"

"

!

documentation

"

    Symbols represent unique strings - every symbol with same printString

    exists exactly once in the system; Symbols are used for selectors, global

    variable-keys etc.

"

! !

!Symbol class methodsFor:'instance creation'!

basicNew:size

    "redefined to return a string instead of a symbol -

     this allows all copy methods inherited from String to

     return strings containing the symbols characters.

     Real symbols are only created with intern: or asSymbol."

    ^ String new:size

!

new:size

    "redefined to return a string instead of a symbol -

     this allows all copy methods inherited from String to

     return strings containing the symbols characters.

     Real symbols are only created with intern: or asSymbol."

    ^ String new:size

!

intern:aString

    "return a unique symbol with printname taken from the String-argument"

%{  /* NOCONTEXT */

    if (__isSymbol(aString)) {

	RETURN (aString);

    }

    if (__isString(aString)) {

    }

%}

.

    ^ self mustBeString

!

fromString:aString

    "same as intern: for Symbol, but may be used to create interned instances

     of subclasses.

     Notice: this fails, if you try to intern an instance of a subclass, AND

     a symbol with the same name already exists. In this case, the original

     symbol is returned. To use it for enum-type symbols, make certain, that the

     names are unique (for example by including the classes name as a prefix-string)."

    |sym len|

    sym := aString asSymbolIfInterned.

    sym notNil ifTrue:[

	^ sym

    ].

    "

     create a new uninterned instance first

    "

    len := aString size.

    sym := super basicNew:len.

    sym replaceFrom:1 to:len with:aString.

    "now, intern it"

%{

    extern OBJ _INTERNSYMBOL();

    sym = _INTERNSYMBOL(sym, (OBJ *)0, __context);

%}.

    ^ sym

!

internCharacter:aCharacter

    "return a unique symbol with printname taken from the Character-argument"

    ^ self intern:(aCharacter asString)

! !

!Symbol class methodsFor:'queries'!

hasInterned:aString ifTrue:trueBlock

    "for ST-80 compatibility - if the argument, aString is known

     as Symbol, evaluate the block with the corresponding symbol

     as argument and return true; otherwise return false"

    |sym|

    (sym := aString asSymbolIfInterned) notNil ifTrue:[

	trueBlock value:sym.

	^ true

    ].

    ^ false

!

hasInterned:aString

    "return true, if the argument, aString is known as Symbol;

     false otherwise"

    ^ aString knownAsSymbol

! !

!Symbol methodsFor:'accessing'!

basicAt:index put:something

    "report an error if interned - interned symbols may not be changed."

    self knownAsSymbol ifTrue:[

	self error:'symbols may not be changed'.

	^ something

    ].

    "

     uninterned - allow change

    "

    ^ super basicAt:index put:something

!

byteAt:index put:value

    "report an error if interned - interned symbols may not be changed."

    ^ self basicAt:index put:(value asCharacter)

! !

!Symbol methodsFor:'copying'!

copy

    "return a copy of myself

     - reimplemented here since symbols are unique"

     ^ self

!

shallowCopy

    "return a copy of myself

     - reimplemented here since symbols are unique"

     ^ self

!

deepCopy

    "return a copy of myself

     - reimplemented here since symbols are unique"

     ^ self

!

deepCopyUsing:aDictionary

    "return a copy of myself

     - reimplemented here since symbols are unique"

     ^ self

!

simpleDeepCopy

    "return a copy of myself

     - reimplemented here since symbols are unique"

     ^ self

! !

!Symbol methodsFor:'converting'!

asString

    "return a string with printname taken from mine"

    ^ self printString

!

asSymbol

    "return the receiver as a symbol.

     Since I am a symbol - just return myself"

    ^ self

!

asSymbolIfInterned

    "return the receiver as a symbol if there is one.

     Since I am a symbol - just return myself"

    ^ self

!

knownAsSymbol 

    "return true if the receiver is known as a symbol.

     Since I am a symbol - just return true"

    ^ true

! !

!Symbol methodsFor:'queries'!

species

    "when copying, or concatenating, return instances of this class"

    ^ String

! 

isSymbol 

    "return true, if the receiver is some kind of symbol.

     Since I am a symbol, return always true"

    ^ true

! !

!Symbol methodsFor:'system primitives'!

become:anotherObject

    "make all references to the receiver become references to anotherObject

     and vice-versa. For symbols, some special action is required, to

     correctly handle a become of the global dictionaries.

     Anyway: this is very dangerous - mysterous side-effects are to be

     expected.

     Notice: because of the danger here, this method may report an error

	     in future versions"

    (Smalltalk includesKey:self) ifTrue:[

	super become:anotherObject.

%{

	__rehashSystemDictionaries();

%}.

    ] ifFalse:[

	super become:anotherObject

    ]

!

becomeNil

    "make all references to the receiver become nil - effectively getting

     rid of the receiver. For symbols, this is not allowed, if the receiver

     is used as a key in some SytemDictionary.

     This can be a very dangerous operation - be warned.

     Notice: because of the danger here, this method may report an error

	     in future versions"

    (Smalltalk includesKey:self) ifTrue:[

	self primitiveFailed

    ] ifFalse:[

	super becomeNil

    ]

! !

!Symbol class methodsFor:'binary storage'!

binaryDefinitionFrom: stream manager: manager

    ^ self intern: (super binaryDefinitionFrom: stream manager: manager)

! !

!Symbol methodsFor:'printing & storing'!

printString

%}

!

printOn:aStream

    "aStream nextPut:$#."

    aStream nextPutAll:self "(self printString)"

!

displayString

    "return a string for displaying the receiver"

    ^ self storeString

!

storeString

    "return a String for storing the receiver"

    (self at:1) isLetter ifTrue:[

	2 to:self size do:[:index |

	    (self at:index) isLetterOrDigit ifFalse:[

		^ '#''' , self , ''''

	    ].

	].

	^ '#' , self

    ].

    ^ '#''' , self , ''''

!

storeOn:aStream

    "store myself on a stream"

    aStream nextPutAll:(self storeString)

! !