how to launch a subset query?

[sunriseXu]

hi, do logica have subset function? I want to compare one set to another, and return a boolean value showing whether the two sets are equal or subset?
eg:
SUBSET({ }, { }) = TRUE
SUBSET({ 1, 2, 3 }, { }) = TRUE
SUBSET({ 1, 2 }, { 1, 2 }) = TRUE
SUBSET({ 1, 2, 3 }, { 1, 2 }) = TRUE
SUBSET({ 1, 3, 5 }, { 1, 2 }) = FALSE
many thanks!

[EvgSkv]

Hello!

We need to check membership in the second list for each element in the first list.
Here is the implementation and a test:

@Engine("sqlite");

# Returns 1 if a is subset of b and 0 otherwise.
# To call as a predicate call Constraint(Subset(a, b)). 
Subset(a, b) = result :-
  result_or_null Min= (e in b :- e in a),
  result == Coalesce(result_or_null, 1);

# Testing Subset function.
Test(a, b, Subset(a, b)) :-
  (a == [], b == [1,2]) |
  (a == [1,2], b == [1,2,3]) |
  (a == [1,2,3], b == [1,2]);

Let me know if you have further questions.