85 lines
2.9 KiB
Factor
85 lines
2.9 KiB
Factor
! Copyright (C) 2007 Gavin Harrison
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! See http://factorcode.org/license.txt for BSD license.
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USING: kernel sequences arrays vectors namespaces math strings
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combinators continuations quotations io assocs ;
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IN: prolog
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SYMBOL: pldb
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SYMBOL: plchoice
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: init-pl ( -- ) V{ } clone pldb set V{ } clone plchoice set ;
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: reset-choice ( -- ) V{ } clone plchoice set ;
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: remove-choice ( -- ) plchoice get pop drop ;
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: add-choice ( continuation -- )
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dup continuation? [ plchoice get push ] [ drop ] if ;
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: last-choice ( -- ) plchoice get pop continue ;
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: rules ( -- vector ) pldb get ;
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: rule ( n -- rule ) dup rules length >= [ drop "No." ] [ rules nth ] if ;
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: var? ( pl-obj -- ? )
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dup string? [ 0 swap nth LETTER? ] [ drop f ] if ;
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: const? ( pl-obj -- ? ) var? not ;
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: check-arity ( pat fact -- pattern fact ? ) 2dup [ length ] 2apply = ;
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: check-elements ( pat fact -- ? ) [ over var? [ 2drop t ] [ = ] if ] 2all? ;
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: (double-bound) ( key value assoc -- ? )
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pick over at* [ pick = >r 3drop r> ] [ drop swapd set-at t ] if ;
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: single-bound? ( pat-d pat-f -- ? )
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H{ } clone [ (double-bound) ] curry 2all? ;
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: match-pattern ( pat fact -- ? )
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check-arity [ 2dup check-elements -rot single-bound? and ] [ 2drop f ] if ;
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: good-result? ( pat fact -- pat fact ? )
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2dup dup "No." = [ 2drop t ] [ match-pattern ] if ;
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: add-rule ( name pat body -- ) 3array rules dup length swap set-nth ;
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: (lookup-rule) ( name num -- pat-f rules )
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dup rule dup "No." = >r 0 swap nth swapd dupd = swapd r> or
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[ dup rule [ ] callcc0 add-choice ] when
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dup number? [ 1+ (lookup-rule) ] [ 2nip ] if ;
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: add-bindings ( pat-d pat-f binds -- binds )
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clone
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[ over var? over const? or
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[ 2drop ] [ rot dup >r set-at r> ] if
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] 2reduce ;
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: init-binds ( pat-d pat-f -- binds ) V{ } clone add-bindings >alist ;
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: replace-if-bound ( binds elt -- binds elt' )
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over 2dup key? [ at ] [ drop ] if ;
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: deep-replace ( binds seq -- binds seq' )
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[ dup var? [ replace-if-bound ]
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[ dup array? [ dupd deep-replace nip ] when ] if
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] map ;
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: backtrace? ( result -- )
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dup "No." = [ remove-choice last-choice ]
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[ [ last-choice ] unless ] if ;
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: resolve-rule ( pat-d pat-f rule-body -- binds )
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>r 2dup init-binds r> [ deep-replace >quotation call dup backtrace?
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dup t = [ drop ] when ] each ;
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: rule>pattern ( rule -- pattern ) 1 swap nth ;
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: rule>body ( rule -- body ) 2 swap nth ;
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: binds>fact ( pat-d pat-f binds -- fact )
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[ 2dup key? [ at ] [ drop ] if ] curry map good-result?
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[ nip ] [ last-choice ] if ;
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: lookup-rule ( name pat -- fact )
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swap 0 (lookup-rule) dup "No." =
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[ nip ]
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[ dup rule>pattern swapd check-arity
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[ rot rule>body resolve-rule dup -roll binds>fact nip ] [ last-choice ] if
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] if ;
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: binding-resolve ( binds name pat -- binds )
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tuck lookup-rule dup backtrace? swap rot add-bindings ;
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: is ( binds val var -- binds ) rot [ set-at ] keep ;
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