29 lines
679 B
Factor
29 lines
679 B
Factor
! Copyright (C) 2008, 2010 Slava Pestov.
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! See http://factorcode.org/license.txt for BSD license.
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USING: kernel accessors ;
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IN: boxes
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TUPLE: box value occupied ;
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: <box> ( -- box ) box new ;
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ERROR: box-full box ;
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: >box ( value box -- )
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dup occupied>>
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[ box-full ] [ t >>occupied (>>value) ] if ; inline
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ERROR: box-empty box ;
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: check-box ( box -- box )
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dup occupied>> [ box-empty ] unless ; inline
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: box> ( box -- value )
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check-box [ f ] change-value f >>occupied drop ; inline
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: ?box ( box -- value/f ? )
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dup occupied>> [ box> t ] [ drop f f ] if ; inline
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: if-box? ( box quot -- )
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[ ?box ] dip [ drop ] if ; inline
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