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listprologprolog-dif

filter list into separate lists

I need to filter the list [#,d,e,#,f,g] such that I get the output as [[d,e],[f,g]] ,
I am stuck while creating a new list every time I encounter '#' is there a way to do this? I tried the code below,

filterL([],List) :-[].
filterL([Head|Tail],X) :-
   (  Head \='#'->
      append(X,Head,List),
      filterL(Tail,List)
   ;  filterL(Tail,X)
   ).
Solution

  • Your problem is not very well defined. Are empty sequences allowed or not? Shall [#] be related to [[],[]] (there is an empty sequence before and after) or []? You say it should be []. So:

    list_splitbyhash(Xs, Xss) :-
   phrase(splitby(Xss,#), Xs).

splitby([],_E) -->
    [].
splitby(Xss,E) -->
    [E],
    splitby(Xss,E).
splitby([Xs|Xss],E) -->
    {Xs = [_|_]},
    all_seq(dif(E),Xs),
    splitby(Xss,E).

all_seq(_, []) --> [].
all_seq(C_1, [C|Cs]) -->
   [C],
   {call(C_1,C)},
   all_seq(C_1, Cs).