This module provides the XSB basics module. The implementation either simply uses SWI-Prolog built-ins and libraries or is copied from the XSB file.

 for(?I, +B1, +B2)

Nondeterministically binds I to all integer values from B1 to B2 inclusive. B1 and B2 must be integers, but either may be larger.

 ith(?Index, +List, ?Element)

Re-exported predicates

The following predicates are exported from this file while their implementation is defined in imported modules or non-module files loaded by this module.

 member(?Elem, ?List)

True if Elem is a member of List. The SWI-Prolog definition differs from the classical one. Our definition avoids unpacking each list element twice and provides determinism on the last element. E.g. this is deterministic:

    member(X, [One]).

author

- Gertjan van Noord

 append(?List1, ?List2, ?List1AndList2)

List1AndList2 is the concatenation of List1 and List2

 select(?Elem, ?List1, ?List2)

Is true when List1, with Elem removed, results in List2. This implementation is determinsitic if the last element of List1 has been selected.

 reverse(?List1, ?List2)

Is true when the elements of List2 are in reverse order compared to List1. This predicate is deterministic if either list is a proper list. If both lists are partial lists backtracking generates increasingly long lists.

 flatten(+NestedList, -FlatList) is det

Is true if FlatList is a non-nested version of NestedList. Note that empty lists are removed. In standard Prolog, this implies that the atom '[]' is removed too. In SWI7, [] is distinct from '[]'.

Ending up needing flatten/2 often indicates, like append/3 for appending two lists, a bad design. Efficient code that generates lists from generated small lists must use difference lists, often possible through grammar rules for optimal readability.

See also

- append/2

 subset(+SubSet, +Set) is semidet

True if all elements of SubSet belong to Set as well. Membership test is based on memberchk/2. The complexity is |SubSet|*|Set|. A set is defined to be an unordered list without duplicates. Elements are considered duplicates if they can be unified.

See also

- ord_subset/2.

Undocumented predicates

The following predicates are exported, but not or incorrectly documented.

 log_ith_new(Arg1, Arg2, Arg3)

 log_ith_to_list(Arg1, Arg2)

 log_ith(Arg1, Arg2, Arg3)

 log_ith_bound(Arg1, Arg2, Arg3)

 memberchk(Arg1, Arg2)

 between(Arg1, Arg2, Arg3)

 comma_append(Arg1, Arg2, Arg3)

 logk_ith(Arg1, Arg2, Arg3, Arg4)

 comma_member(Arg1, Arg2)

 comma_length(Arg1, Arg2)

 comma_to_list(Arg1, Arg2)

 comma_memberchk(Arg1, Arg2)

 abscomma_memberchk(Arg1, Arg2)