[英]Define a predicate inside a predicate in prolog
我正在嘗試將謂詞內聯定義為將其傳遞給Prolog中的另一個謂詞。
% Test if a "product" of graphs G1 and G2 has a "mini-loop" starting from Q
test_property_combined(G1,G2,Q):-
(g12(Q1,Q2) :- combine(G1,G2,Q1,Q2)),
some_property(g12,Q).
(上面的語法顯然是錯誤的。)
后來, g12
將通過調用call
% Test if a graph G has a "mini-loop" starting from Q
some_property(G,Q):-
Goal1 =.. [G,Q,C],
Goal2 =.. [G,C,Q],
call(Goal1),
call(Goal2).
問題仍然存在,因為我想在某種先前定義的謂詞聚合上測試some_property
。
% Create a "product" of graphs G1 and G2
combine(G1,G2,(Q1,Q2),(Q3,Q4)):-
Goal1 =.. [G1,Q1,Q3],
Goal2 =.. [G2,Q2,Q4],
call(Goal1),
call(Goal2).
提到的謂詞和測試查詢的示例:
% g1 and g2 are graphs
g1(a,b).
g1(b,a).
g2(c,d).
g2(d,c).
?- test_property_combined(g1,g2,(a,c)).
怎么去做呢?
我不確定這一點,但這有效:
test_property_combined(G1,G2,Q):-
assert((g12(Q1,Q2) :- combine(G1,G2,Q1,Q2))),
some_property(g12,Q).
好吧,可能是那樣的
:- use_module(library(lambda)).
test_property_combined(G1,G2,Q):-
% (g12(Q1,Q2) :- combine(G1,G2,Q1,Q2)),
Pred = \Z^T^combine(G1,G2,Z,T),
some_property(Pred,Q).
combine(G1,G2,(Q1,Q2),(Q3,Q4)):-
Goal1 =.. [G1,Q1,Q3],
Goal2 =.. [G2,Q2,Q4],
call(Goal1),
call(Goal2).
some_property(G,Q):-
call(G, Q, C),
call(G, C, Q).
最后編輯(希望如此),完整代碼:
test_property_combined(G1,G2,Q):-
some_property(combine(G1,G2),Q).
combine(G1,G2,(Q1,Q2),(Q3,Q4)):-
call(G1,Q1,Q3),
call(G2,Q2,Q4).
some_property(G,Q):-
call(G, Q, C),
call(G, C, Q).
g1(a,b).
g1(b,a).
g2(c,d).
g2(d,c).
@false =>有用的評論,像往常一樣!
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