CODEWITHSUNDEEP
prolog
Stranger
Stranger

Reputation: 862

Subset function in prolog

I am working on writing a subset function and I have succeeded in doing so. Here's my function which implements member function: 

 member( X, [ X | T ] ).
 member( X, [ _ | T ] ) :- member( X, T ).

 subset([], _).
 subset([H|T1], T2) :-
    member(H, T2),
    subset(T1, T2). 
 subset([H1|T1], [H2|T2]) :-
    \+ member(H1, T2),
    subset([H1|T1], T2).

My question is, is there a better way to write this function using the member function of course.

Upvotes: 1

Views: 1334

Answers (1)

gusbro
gusbro

Reputation: 22585

The third clause of subset/3 does not make sense and i think that it should be removed. If H1 is not a member of T2, then the recursive call subset([H1|T1], T2) will obviously don't succeed either.

Aside from that, the first two clauses seem the way to go.

Upvotes: 2

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