dividing a list up to a point in prolog

Question

my_list([this,is,a,dog,.,are,tigers,wild,animals,?,the,boy,eats,mango,.]).

suppose this is a list in prolog which i want to divide in three parts that is up to three full stops and store them in variables.

how can i do that...

counthowmany(_, [], 0) :- !.
counthowmany(X, [X|Q], N) :- !, counthowmany(X, Q, N1), N is N1+1.
counthowmany(X, [_|Q], N) :- counthowmany(X, Q, N).
number_of_sentence(N) :- my_list(L),counthowmany(.,L,N).

i already counted the number of full stops in the list(my_list) now i want to divide the list up to first full stop and store it in a variable and then divide up to second full stop and store in a variable and so on.........

Answer 1

Your problem statement did not specify what a sequence without a dot should correspond to. I assume that this would be an invalid sentence - thus failure.

:- use_module(library(lambda)).

list_splitted(Xs, Xss) :-
   phrase(sentences(Xss), Xs).

sentences([]) --> [].
sentences([Xs|Xss]) -->
   sentence(Xs),
   sentences(Xss).

sentence(Xs) -->
   % {Xs = [_|_]},  % add this, should empty sentences not be allowed
   allseq(dif('.'),Xs),
   ['.'].

% sentence(Xs) -->
%    allseq(\X^maplist(dif(X),['.',?]), Xs),
%    (['.']|[?]).

allseq(_P_1, []) --> [].
allseq( P_1, [C|Cs]) -->
   [C],
   {call(P_1,C)},
   allseq(P_1, Cs).

Answer 2

UPDATE: the code slightly simplified after @CapelliC comment.

One of the many ways to do it (another, better way - is to use DCG - definite clause grammar):

You don't really need counthowmany.

split([], []).
split(List, [Part | OtherParts]) :-
    append(Part, ['.' | Rest], List),
    split(Rest, OtherParts).

Let's try it:

?- my_list(List), split(List, Parts).
List = [this, is, a, dog, '.', tigers, are, wild, animals|...],
Parts = [[this, is, a, dog], [tigers, are, wild, animals], [the, boy, eats, mango]] 

Answer 3

In this answer we define split_/2 based on splitlistIf/3 and list_memberd_t/3:

split_(Xs, Yss) :-
   splitlistIf(list_memberd_t(['?','.','!']), Xs, Yss).

Sample queries:

?- _Xs = [this,is,a,dog,'.', are,tigers,wild,animals,?, the,boy,eats,mango,'.'], 
   split_(_Xs, Yss).
Yss = [  [this,is,a,dog]   ,[are,tigers,wild,animals] ,[the,boy,eats,mango]   ].

?- split_([a,'.',b,'.'], Yss).
Yss = [[a],[b]].            % succeeds deterministically