CODEWITHSUNDEEP
prolog
Tamos
Tamos

Reputation: 39

How to return the list that contains a certain element in Prolog?

I'm learning prolog but I have a problem with a code. I want to check if an element exists in a list of lists and if it exists I want to get the list that contains that element to manipulate the list. I made a clause to prove that the element is or not in the list of lists but I don't know how to get that list, please help me.

memberlist(X,[H|_]) :-
    member(X,H).
memberlist(X,[_|T2]) :-
  memberlist(X,T2).

I do this query:

memberlist("product1",[["product2", 100, "available"],["product3", 100, "sold out"],["product1", 200, "available"]]).

and I get: true but also I want to get the list that contains the string "product1" so the result that I'm looking for is: ["product1", 200, "available"]

Upvotes: 0

Views: 159

Answers (1)

14241354
14241354

Reputation: 211

How about introducing a third argument to store the matching list? e.g.:

memberlist(X,[H|_],H) :-
  member(X,H).
memberlist(X,[_|T2],Y) :-
  memberlist(X,T2,Y).

Example query:

memberlist("product1", [["product2", 100, "available"],["product3", 100, "sold out"],["product1", 200, "available"]], Result).

Produces the outcome:

Result = ["product1", 200, "available"]

Upvotes: 1

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