64 lines
1.5 KiB
Plaintext
64 lines
1.5 KiB
Plaintext
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% This file has been included as an YAP library by Vitor Santos Costa, 2013
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% it implements a very simple interval solver designed to interact with the exo
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% data-base.
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% It assumes simple queries and a contiguous interval,
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% and does not really expect to do non-trivial
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% constraint propagation and solving.
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:- module(exo_interval,
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[max/2,
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min/2,
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(#<)/2,
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(#>)/2,
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(#=)/2,
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op(700, xfx, (#>)),
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op(700, xfx, (#<)),
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op(700, xfx, (#=))]).
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:- meta_predicate
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max(?,0),
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min(?,0).
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max(X, G) :-
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attvar(X),
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get_attr(X, exo_interval, Atts), !,
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throw(error('cannot handle combination of attributes ')).
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max(X, G) :-
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var(X),
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put_attr(X, exo_interval, max),
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call(G).
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min(X, G) :-
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attvar(X),
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get_attr(X, exo_interval, Atts), !,
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throw(error('cannot handle combination of attributes ')).
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min(X, G) :-
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var(X),
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put_attr(X, exo_interval, min),
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call(G).
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X #> Y :-
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( var(X) -> put_attr(X, exo_interval, '>'(Y) ) ; true ),
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( var(Y) -> put_attr(X, exo_interval, '<'(X) ) ; true ),
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when((nonvar(X), nonvar(Y)), X > Y).
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X #< Y :-
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( var(X) -> put_attr(X, exo_interval, '<'(Y) ) ; true ),
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( var(Y) -> put_attr(X, exo_interval, '>'(X) ) ; true ),
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when((nonvar(X), nonvar(Y)), X < Y).
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X #= Y :-
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X = Y,
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( var(X) -> put_attr(X, exo_interval, '='(Y) ) ; true ).
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attribute_goals(X) -->
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{ get_attr(X, exo_interval, Op) },
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( { Op = max } -> [max(X)] ;
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{ Op = min } -> [min(X)] ;
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{ Op = '>'(Y) } -> [X #> Y] ;
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{ Op = '<'(Y) } -> [X #< Y] ;
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{ Op = '='(Y) } -> [X #= Y] ).
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