26 lines
782 B
Factor
26 lines
782 B
Factor
! Copyright (C) 2004, 2005 Slava Pestov.
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! See http://factor.sf.net/license.txt for BSD license.
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IN: generic
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USING: errors hashtables kernel lists namespaces parser
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sequences strings words vectors ;
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! Union metaclass for dispatch on multiple classes.
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SYMBOL: union
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: union-predicate ( members -- list )
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[
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"predicate" word-prop
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[ dup ] swap add [ drop t ] cons
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] map [ drop f ] swap alist>quot ;
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: set-members ( class members -- )
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2dup [ types ] map concat "types" set-word-prop
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"members" set-word-prop ;
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: define-union ( class predicate members -- )
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#! We have to turn the f object into the f word, same for t.
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3dup nip set-members pick union define-class
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union-predicate define-predicate ;
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PREDICATE: word union metaclass union = ;
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