/*** This module provides unordered sets. The unordered sets are* represented by lists [x1, .., xn]. The lists need not to be* ordered or duplicate free. But the provided operations do not* necessarily preserve duplicates:** Examples:* ?- union([2,3,4], [1,2,4,5], X).* X = [3,1,2,4,5]* ?- union([1,2,4,5], [2,3,4], X).* X = [1,5,2,3,4]** The realization uses a membership check based on (==)/2. As a* result the predicates are safe to be used with non-ground terms.* On the other hand, since this comparison is not arithmetical,* 1 and 1.0 are for example considered different.** Warranty & Liability* To the extent permitted by applicable law and unless explicitly* otherwise agreed upon, XLOG Technologies GmbH makes no warranties* regarding the provided information. XLOG Technologies GmbH assumes* no liability that any problems might be solved with the information* provided by XLOG Technologies GmbH.** Rights & License* All industrial property rights regarding the information - copyright* and patent rights in particular - are the sole property of XLOG* Technologies GmbH. If the company was not the originator of some* excerpts, XLOG Technologies GmbH has at least obtained the right to* reproduce, change and translate the information.** Reproduction is restricted to the whole unaltered document. Reproduction* of the information is only allowed for non-commercial uses. Selling,* giving away or letting of the execution of the library is prohibited.* The library can be distributed as part of your applications and libraries* for execution provided this comment remains unchanged.** Restrictions* Only to be distributed with programs that add significant and primary* functionality to the library. Not to be distributed with additional* software intended to replace any components of the library.** Trademarks* Jekejeke is a registered trademark of XLOG Technologies GmbH.*/* contains(E, S):* The predicate succeeds when the set S contains the element E.*/% contains(+Elem, +Set)* remove(E, S, T):* The predicate succeeds when the set S contains the element E* and T is the set without the element.*/% remove(+Elem, +Set, -Set)* difference(S1, S2, S3):* The predicate succeeds when S3 unifies with the difference of S1 by S2.*/% difference(+Set, +Set, -Set)* intersection(S1, S2, S3):* The predicate succeeds when S3 unifies with the intersection of S1 and S2.*/% intersection(+Set, +Set, -Set)* union(S1, S2, S3):* The predicate succeeds when S3 unifies with the union of S1 and S2.*/% union(+Set, +Set, -Set)* subset(S1, S2):* The predicate succeeds when S1 is a subset of S2.*/% subset(+Set, +Set)* permutation(S1, S2):* The predicate succeeds when S1 is a permutation of S2.*/% permutation(+Set, +Set)