! :folding=indent:collapseFolds=1:

! $Id$
!
! Copyright (C) 2004 Slava Pestov.
! 
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! modification, are permitted provided that the following conditions are met:
! 
! 1. Redistributions of source code must retain the above copyright notice,
!    this list of conditions and the following disclaimer.
! 
! 2. Redistributions in binary form must reproduce the above copyright notice,
!    this list of conditions and the following disclaimer in the documentation
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! THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
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IN: lists
USE: kernel

! An association list is a list of conses where the car of each
! cons is a key, and the cdr is a value. See the Factor
! Developer's Guide for details.

: assoc? ( list -- ? )
    #! Push if the list appears to be an alist.
    dup list? [ [ cons? ] all? ] [ drop f ] ifte ;

: assoc* ( key alist -- [ key | value ] )
    #! Looks up the key in an alist. Push the key/value pair.
    #! Most of the time you want to use assoc not assoc*.
    dup [
        2dup car car = [ nip car ] [ cdr assoc* ] ifte
    ] [
        2drop f
    ] ifte ;

: assoc ( key alist -- value )
    #! Looks up the key in an alist.
    assoc* dup [ cdr ] when ;

: remove-assoc ( key alist -- alist )
    #! Remove all key/value pairs with this key.
    [ dupd car = not ] subset nip ;

: acons ( value key alist -- alist )
    #! Adds the key/value pair to the alist. Existing pairs with
    #! this key are not removed; the new pair simply shadows
    #! existing pairs.
    >r swons r> cons ;

: set-assoc ( value key alist -- alist )
    #! Adds the key/value pair to the alist.
    dupd remove-assoc acons ;

: assoc-apply ( value-alist quot-alist -- )
    #! Looks up the key of each pair in the first list in the
    #! second list to produce a quotation. The quotation is
    #! applied to the value of the pair. If there is no
    #! corresponding quotation, the value is popped off the
    #! stack.
    swap [
        over >r unswons rot assoc* dup [
            cdr call
        ] [
            2drop
        ] ifte r>
    ] each drop ;