[英]how to prevent no in prolog?
Prolog, recursive function: i want it to print the C with each element of the list for example: C=30 and [H|T]= [-9,-10,-30] Prolog,递归函数:我希望它用列表的每个元素打印C,例如:C = 30和[H | T] = [-9,-10,-30]
myfunc(C,[H|T]):-
(\+([H|T]=[])),
write(C), write(' with '), write(H), nl,
myfunc(C,T).
i check at the beginning that the head of the list is not empty. 我首先检查列表的开头是否为空。 it gives me this output 它给了我这个输出
30 with -9
30 with -10
30 with -30
(32 ms) no
this output is what i want but i dont want to get a 'no' at the end because this makes the parent function to fail as well! 此输出是我想要的,但我不想在最后得到“ no”,因为这会使父函数也失败! how can i remove it and put a 'yes' instead? 我如何将其删除并改为“是”?
Simple way: just add a base case with the empty list. 简单方法:只需添加一个带有空列表的基本案例。
myfunc(_, []) :- !.
myfunc(C,[H|T]):-
write(C), write(' with '), write(H), nl,
myfunc(C,T).
test: 测试:
?- myfunc(30, [1, 2, 3]).
30 with 1
30 with 2
30 with 3
true.
I don't know if this is the best way to do that, but you didn't give us much details about your whole program, so I opted for a small modification of your predicate. 我不知道这是否是最好的方法,但是您没有为我们提供有关整个程序的详细信息,因此我选择对谓词进行一些小的修改。
If you have maplist in your Prolog, you can write 如果您的Prolog中有地图列表,则可以编写
myfunc(N, L) :-
maplist(my_write(N), L).
my_write(N, Val) :-
format('~w with ~w~n', [N, Val]).
With SWI-Prolog and module lambda 带有SWI-Prolog和模块lambda
:- use_module(library(lambda)).
myfunc(N, L) :-
maplist(\X^format('~w with ~w~n', [N, X]), L).
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