"

 COPYRIGHT (c) 2002 by eXept Software AG

              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:libbasic2' }"

SequenceableCollection subclass:#Cons

	instanceVariableNames:'car cdr'

	classVariableNames:''

	poolDictionaries:''

	category:'Collections-Linked'

!

!Cons class methodsFor:'documentation'!

copyright

"

 COPYRIGHT (c) 2002 by eXept Software AG

              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

"

    A pair as in lisp.

    Create with:

        a !! b

    or:

        Cons car:a cdr:b

    Conses are not heavily used by Smalltalk (actually: not at all).

    Consider this mostly a demo class.

    [author:]

        Claus Gittinger

    [see also:]

"

! !

!Cons class methodsFor:'instance creation'!

car:carArg cdr:cdrArg

    ^ self basicNew car:carArg cdr:cdrArg

!

fromArray:anArray

    |p last first|

    anArray do:[:el |

        p := self car:el cdr:nil.

        first isNil ifTrue:[

            first := p.

        ] ifFalse:[

            last cdr:p.

        ].

        last := p.

    ].

    ^ first.

    "

     Cons fromArray:#(1 2 3 4)   

     Cons fromArray:#()    

     Cons fromArray:#(1)    

    "

! !

!Cons methodsFor:'accessing'!

at:n

    "for collection compatibility:

     a slow indexed accessor"

    ^ (self nth:n) car

    "

     (Cons fromArray:#(1))       at:1     

     (Cons fromArray:#(1 2 3 4)) at:1 

     (Cons fromArray:#(1 2 3 4)) at:3  

     (Cons fromArray:#(1 2 3 4)) at:4  

     (Cons fromArray:#(1 2 3 4)) at:5  

    "

!

at:n put:newValue

    "for collection compatibility:

     a slow indexed accessor"

    (self nth:n) car:newValue.

    ^ newValue.

    "

     |l|

     l := Cons fromArray:#(1 2 3 4).

     l at:1 put:'one'.

     l at:3 put:'three'.

     l       

    "

!

last

    "for lispers:

     return the last element of a list"

    |p rest|

    p := self.

    [(rest := p cdr) notNil] whileTrue:[

        p := rest

    ].

    "

     (Cons fromArray:#(1))       last     

     (Cons fromArray:#(1 2 3 4)) last    

    "

!

nth:n

    "for lispers:

     return the nth element of a list"

    |cnt p|

    cnt := n.

    p := self.

    [true] whileTrue:[

        cnt := cnt - 1.

        p := p cdr.

        p isNil ifTrue:[

            self error:'no such element' mayProceed:true.

            ^ nil

        ].

    ].

    "

     (Cons fromArray:#(1))       nth:1     

     (Cons fromArray:#(1 2 3 4)) nth:1 

     (Cons fromArray:#(1 2 3 4)) nth:3  

     (Cons fromArray:#(1 2 3 4)) nth:4  

     (Cons fromArray:#(1 2 3 4)) nth:5  

    "

! !

!Cons methodsFor:'accessing - basic'!

car

    "return the head, first or car - whatever you wonna call it"

    ^ car

!

car:something

    "set the head, first or car - whatever you wonna call it"

    car := something.

!

car:carArg cdr:cdrArg 

    "set both car and cdr"

    car := carArg.

    cdr := cdrArg.

!

cdr

    "return the tail, second or cdr - whatever you wonna call it"

    ^ cdr

!

cdr:something

    "set the tail, second or cdr - whatever you wonna call it"

    cdr := something.

! !

!Cons methodsFor:'list processing'!

append:aCons

    "for lispers:

     append the arg. Return a new list, where the 2nd part is shared"

    |p rest|

    p := self.

    [(rest := p cdr) notNil] whileTrue:[

        p := rest

    ].

    p cdr:aCons.

    ^ self

    "

     (Cons fromArray:#(1 2 3 4)) 

        append:(Cons fromArray:#(5 6 7 8)) 

    "

    "sharing demonstrated:

     |a b ab|

     a := Cons fromArray:#(1 2 3 4).

     b := Cons fromArray:#(5 6 7 8).

     ab := a append:b.

     b car:'five'.

     ab    

    "

! !

!Cons methodsFor:'printing'!

displayString

    ^ self printString

!

printOn:aStream

    (car isLazyValue not and:[ car isCons ]) ifTrue:[

        aStream nextPutAll:'('.

        car printOn:aStream.

        aStream nextPutAll:')'.

    ] ifFalse:[

        car printOn:aStream.

    ].

    aStream nextPutAll:'!!'.

    (cdr isLazyValue not and:[ cdr isCons ]) ifTrue:[

        aStream nextPutAll:'('.

        cdr printOn:aStream.

        aStream nextPutAll:')'.

    ] ifFalse:[

        cdr printOn:aStream.

    ].

! !

!Cons methodsFor:'queries'!

isCons

    ^ true

!

size

    "for smalltalkers: the lists length"

    |l p rest|

    l := 1.

    p := self.

    [(rest := p cdr) notNil] whileTrue:[

        l := l + 1.

        p := rest

    ].

    ^ l

    "

     (Cons fromArray:#( )) size    

     (Cons fromArray:#(1)) size     

     (Cons fromArray:#(1 2 3 4)) size    

    "

! !

!Cons class methodsFor:'documentation'!

version

! !