45 lines
979 B
Factor
45 lines
979 B
Factor
! Copyright (C) 2005, 2006 Slava Pestov.
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! See http://factorcode.org/license.txt for BSD license.
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IN: queues
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USING: errors kernel ;
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TUPLE: entry obj next ;
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C: entry ( obj -- entry ) [ set-entry-obj ] keep ;
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TUPLE: queue head tail ;
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C: queue ( -- queue ) ;
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: queue-empty? ( queue -- ? ) queue-head not ;
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: clear-queue ( queue -- )
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f over set-queue-head f swap set-queue-tail ;
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: (enque) ( entry queue -- )
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[ set-queue-head ] 2keep set-queue-tail ;
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: enque ( elt queue -- )
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>r <entry> r> dup queue-empty? [
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(enque)
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] [
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[ queue-tail set-entry-next ] 2keep set-queue-tail
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] if ;
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: (deque) ( queue -- )
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dup queue-head over queue-tail eq? [
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clear-queue
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] [
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dup queue-head entry-next swap set-queue-head
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] if ;
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TUPLE: empty-queue ;
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: empty-queue ( -- * ) <empty-queue> throw ;
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: deque ( queue -- elt )
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dup queue-empty? [
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empty-queue
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] [
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dup queue-head entry-obj >r (deque) r>
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] if ;
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