"

 COPYRIGHT (c) 1995 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.

"

"{ Package: 'stx:libbasic' }"

Array variableSubclass:#ImmutableArray

	instanceVariableNames:''

	classVariableNames:''

	poolDictionaries:''

	category:'System-Compiler-Support'

!

!ImmutableArray class methodsFor:'documentation'!

copyright

"

 COPYRIGHT (c) 1995 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.

"

!

documentation

"

    By default, array literals in smalltalk are mutable objects. That

    may lead to some subtle (and hard to find errors), if some method passes

    a literal array constant as argument to someone else, who changes the

    array using at:put: like messages. Since the array object is kept in

    the first methods literals, the array constant has now been changed without

    having the method's sourcecode reflect this. Thus, the method will

    behave differently from what its source may make you think.

    To help finding this kind of 'feature/bug', the compiler can be

    configured to create instances of this ImmutableArray instead of Arrays

    for array literals. Instances of ImmutableArray catch storing accesses and

    enter the debugger. Although useful, this feature is disabled by default

    for compatibility to other smalltalk implementations.

    (Also, if turned on, this makes inspecting array literals entered in

     a workspace somewhat strange: you cannot modify it any longer).

    Turn the ImmutableArray feature on by setting the Parsers class variable

    'ArraysAreImmutable' to true or use the new launchers settings menu.

    ATTENTION:

	there may be still code around which checks for explicit class being Array

	(both in Smalltalk and in primitive code). All code like foo 'class == Array'

	or '__isArray' will not work with ImmutableArrays.

	A somewhat better approach would be to either add a flag to the object (mutability)

	and check this dynamically (expensive) or to place immutable objects into a readonly

	memory segment (the good solution). We will eventually implement the second in the future...

    [see also:]

	ImmutableString

	Parser Scanner

    [author:]

	Claus Gittinger

"

! !

!ImmutableArray methodsFor:'accessing'!

at:index put:value

    "Trigger an error if an immutable array is stored into.

     The store will be performed (for compatibility reasons) if you continue

     in the debugger."

    self noModificationError.

    ^ super at:index put:value

    "Modified: / 3.8.1998 / 14:45:23 / cg"

!

basicAt:index put:value

    "Trigger an error if an immutable array is stored into.

     The store will be performed (for compatibility reasons) if you continue

     in the debugger."

    self noModificationError.

    ^ super basicAt:index put:value

    "Modified: / 3.8.1998 / 14:45:30 / cg"

! !

!ImmutableArray methodsFor:'converting'!

asImmutableArray

    ^ self

! !

!ImmutableArray methodsFor:'copying'!

copyEmpty

    "when copying, return a real (mutable) Array"

    ^ Array new:self size

!

copyEmptyAndGrow:size

    "when copying, return a real (mutable) Array"

    ^ Array new:size

!

postCopy

    "when copied, make it me a real (mutable) Array"

    self changeClassTo:Array.

!

postDeepCopy

    "when copied, make it me a real (mutable) Array"

    self changeClassTo:Array.

!

shallowCopy

    "when copying, return a real (mutable) Array"

    |sz|

    sz := self size.

    ^ (Array new:sz)

	replaceFrom:1 to:sz with:self startingAt:1

! !

!ImmutableArray methodsFor:'private'!

species

    "Copies should be mutable"

    ^ Array

! !

!ImmutableArray methodsFor:'queries'!

isLiteral

    "return true, if the receiver can be used as a literal constant in ST syntax

     (i.e. can be used in constant arrays)"

    "yes, I must be"

    ^ true

! !

!ImmutableArray methodsFor:'specials'!

become:anotherObject

    "trigger an error if I should become something else

     (this would be an even more tricky manipulation)"

    self noModificationError.

    ^ super become:anotherObject

!

becomeNil

    "trigger an error if I should become nil

     (this would be an even more tricky manipulation)"

    self noModificationError.

    ^ super becomeNil

! !

!ImmutableArray class methodsFor:'documentation'!

version

!

version_CVS

! !