120 lines
3.7 KiB
Prolog
120 lines
3.7 KiB
Prolog
:- module(atts, [attribute/1, absent_attr/2, get_attr/2, put_attr/2,
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absent_from_list/2, get_from_list/2, add_to_list/2,
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del_attr/3, del_attr_step/2, del_attr_non_head/3]).
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:- use_module(library(control)).
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:- use_module(library(dcgs)).
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:- use_module(library(terms)).
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:- op(1199, fx, attribute).
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absent_attr(V, Attr) :-
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'$get_attr_list'(V, Ls),
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absent_from_list(Ls, Attr).
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absent_from_list(X, _) :-
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var(X), !.
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absent_from_list([L|Ls], Attr) :-
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( L \= Attr -> absent_from_list(Ls, Attr) ).
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get_attr(V, Attr) :-
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'$get_attr_list'(V, Ls), nonvar(Ls), get_from_list(Ls, Attr).
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get_from_list([L|Ls], Attr) :-
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nonvar(L),
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( L \= Attr -> nonvar(Ls), get_from_list(Ls, Attr)
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; copy_term(L, L0), L0 = Attr
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; get_from_list(Ls, Attr)
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).
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put_attr(V, Attr) :-
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'$get_attr_list'(V, Ls), add_to_list(Ls, Attr).
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add_to_list(Ls, Attr) :-
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( var(Ls) -> Ls = [Attr | _]
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; Ls = [_ | Ls0] -> add_to_list(Ls0, Attr)
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).
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del_attr(Ls0, _, _) :-
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var(Ls0), !.
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del_attr(Ls0, V, Attr) :-
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Ls0 = [Att | Ls1],
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nonvar(Att),
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( Att \= Attr -> del_attr_non_head(Ls0, Ls1, Attr)
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; '$del_attr_head'(V), del_attr(Ls1, V, Attr)
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).
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del_attr_step(Ls1, Attr) :-
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( nonvar(Ls1) -> Ls1 = [_ | Ls2], del_attr_non_head(Ls1, Ls2, Attr)
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; true ).
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%% assumptions: Ls0 is a list, Ls1 is its tail;
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%% the head of Ls0 can be ignored.
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del_attr_non_head(Ls0, Ls1, Attr) :-
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Ls0 = [_, Att | _],
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nonvar(Att),
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!,
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( Att \= Attr -> del_attr_step(Ls1, Attr)
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; '$del_attr'(Ls0), %% set tail of Ls0 = tail of Ls1. can be undone by backtracking.
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del_attr_step(Ls1, Attr)
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).
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del_attr_non_head(_, _, _).
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user:term_expansion(Term0, Terms) :-
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nonvar(Term0),
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Term0 = (:- attribute Atts),
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nonvar(Atts),
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phrase(put_attrs_var_check, Terms, Terms1),
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phrase(put_attrs(Atts), Terms1, Terms2),
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phrase(get_attrs_var_check, Terms2, Terms3),
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phrase(get_attrs(Atts), Terms3).
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put_attrs_var_check -->
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{ numbervars([Var, Attr], 0, _) },
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[(put_atts(Var, Attr) :- nonvar(Var), throw(error(type_error(variable, Var), put_atts/2))),
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(put_atts(Var, Attr) :- var(Attr), throw(error(instantiation_error, put_atts/2)))].
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get_attrs_var_check -->
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{ numbervars([Var, Attr], 0, _) },
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[(get_atts(Var, Attr) :- nonvar(Var), throw(error(type_error(variable, Var), get_atts/2))),
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(get_atts(Var, Attr) :- var(Attr), !, '$get_attr_list'(Var, Attr))].
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put_attrs(Name/Arity) -->
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put_attr(Name, Arity),
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{ numbervars([Var, Attr], 0, _) },
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[(put_atts(Var, Attr) :- lists:maplist(put_atts(Var), Attr))].
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put_attrs((Name/Arity, Atts)) -->
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{ nonvar(Atts) },
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put_attr(Name, Arity),
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put_attrs(Atts).
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get_attrs(Name/Arity) -->
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get_attr(Name, Arity).
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get_attrs((Name/Arity, Atts)) -->
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{ nonvar(Atts) },
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get_attr(Name, Arity),
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get_attrs(Atts).
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put_attr(Name, Arity) -->
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{ functor(Attr, Name, Arity),
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numbervars(Attr, 0, Arity),
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V = '$VAR'(Arity) },
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[(put_atts(V, +Attr) :- !, functor(Attr, _, _), put_attr(V, Attr)),
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(put_atts(V, Attr) :- !, functor(Attr, _, _), put_attr(V, Attr)),
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(put_atts(V, -Attr) :- !, functor(Attr, _, _), '$get_attr_list'(V, Ls), del_attr(Ls, V, Attr))].
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get_attr(Name, Arity) -->
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{ functor(Attr, Name, Arity),
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numbervars(Attr, 0, Arity),
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V = '$VAR'(Arity) },
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[(get_atts(V, +Attr) :- !, functor(Attr, _, _), get_attr(V, Attr)),
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(get_atts(V, Attr) :- !, functor(Attr, _, _), get_attr(V, Attr)),
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(get_atts(V, -Attr) :- !, functor(Attr, _, _), absent_attr(V, Attr))].
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user:goal_expansion(Term, M:put_atts(Var, Attr)) :-
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nonvar(Term),
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Term = put_atts(Var, M, Attr).
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user:goal_expansion(Term, M:get_atts(Var, Attr)) :-
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nonvar(Term),
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Term = get_atts(Var, M, Attr).
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