计算Prolog中一个列表中出现次数的方法 [英] Method that counts the number of occurs in one list in Prolog

问题描述

我必须编写一个方法来计算一个列表从另一个给定列表中出现的次数.例如:

I have to write a method that can count the number of occurrences of one list from another list given. For example:

?-reps([a,b,c,a,b,c],[a,b,c],0,R). 
R = 2 ? ;
no

我正在尝试编码:

incr(X, X1) :-
   X1 is X+1.

reps([],[],C,D):-
   incr(C,D).
reps(_,[],C,D):-
   incr(C,D),
   !.
reps([X|A],[X|B],C,D):-
   reps(A,B,C,D),
   reps(A,B,C,D).

我的主要问题是，我可以比较第一次，但第二次我的比较列表"却无法进行比较.现在是空的，我无法比较列表的其余部分.有没有办法制作一个可以存储比较列表"的全局变量?之后调用它?

My main problem is that, I can compare the first time, but the second time my "comparation list" is now empty and I can't compare the rest of the list. Is there a way to make a global variable that can store the "comparation list" to call it after?

推荐答案

我的解决方案，假设空模板意味着无限多次重复:

My solution, assumes empty template implies infinitely many repetitions:

reps(L, [], inf):-
  is_proper_list(L).
reps(L, Template, N):-
  dif(Template, []),
  reps(L, Template, 0, N).
  
reps([], _, N, N).
reps(L, Template, N, N2):-
  starts_with(Template, L, L1),
  dif(N, N2),
  succ(N, N1),
  reps(L1, Template, N1, N2).
reps([A|L], Template, N, N1):-
  split_l(Template, [A|L], H, C),
  reps1(C, L, Template, H, N, N1).

reps1(y, L, Template, H, N, N1):-
  dif(Template, H),
  reps(L, Template, N, N1).
reps1(n, _, _, _, N, N).

starts_with([], L, L).
starts_with([A|T], [A|L], L1):-
  starts_with(T, L, L1).
  
split_l([], _, [], y).
split_l([_|_], [], [], n).
split_l([_|T], [A|L], [A|L1], C):-
  split_l(T, L, L1, C).
  
is_proper_list(L):-
  freeze(L, is_proper_list1(L)).

is_proper_list1([]).
is_proper_list1([_|L]):- acyclic_term(L), is_proper_list(L).

一些示例运行:

?- reps([a,b,c,a,b,c],[a,b,c],N). 
N = 2 ;
false.

?- reps([a,b,c,a,b,c],X,2).
X = [a] ;
X = [a, b] ;
X = [a, b, c] ;
X = [b] ;
X = [c] ;
X = [b, c] ;
false.

?- reps([a,B],[B],N).
B = a,
N = 2 ;
N = 1,
dif(B, a) ;
;
false.

?- reps([A,B,C],[D,E],N).
A = D,
B = E,
N = 1 ;
B = D,
C = E,
N = 1,
dif(f(D, E), f(A, D)) ;
;
N = 0,
dif(f(D, E), f(A, B)),
dif(f(D, C), f(B, E)) ;
;
false.


?- reps(L,T,N).
T = [],
N = inf,
freeze(L, is_proper_list1(L)) ;
;
L = [],
N = 0,
dif(T, []) ;
;
L = T, T = [_1740],
N = 1 ;
L = [_1740, _1740],
T = [_1740],
N = 2 ;
L = [_1740, _1740, _1740],
T = [_1740],
N = 3 .
 ...

更多示例:

?- reps([], [], N).
N = inf ;
false.

?- reps(L, [], N).
N = inf,
freeze(L, is_proper_list1(L)) ;
;
false.

?- reps(L, [], N), L=[].
L = [],
N = inf ;
false.

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