21 lines
413 B
Factor
Executable File
21 lines
413 B
Factor
Executable File
! Copyright (C) 2008 William Schlieper
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! See http://factorcode.org/license.txt for BSD license.
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USING: kernel continuations sequences namespaces fry ;
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IN: backtrack
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SYMBOL: failure
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: amb ( seq -- elt )
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failure get
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'[ , _ '[ , '[ failure set , , continue-with ] callcc0 ] each
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, continue ] callcc1 ;
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: fail ( -- )
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f amb drop ;
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: require ( ? -- )
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[ fail ] unless ;
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