sets

20002023 Ericsson AB. All Rights Reserved. Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. sets Robert Virding Bjarne Däcker 1 Bjarne Däcker 1999-07-27 A sets.xml

sets Functions for set manipulation.

Sets are collections of elements with no duplicate elements.

The data representing a set as used by this module is to be regarded as opaque by other modules. In abstract terms, the representation is a composite type of existing Erlang terms. See note on data types. Any code assuming knowledge of the format is running on thin ice.

This module provides the same interface as the ordsets(3) module but with an undefined representation. One difference is that while this module considers two elements as different if they do not match (=:=), ordsets considers two elements as different if and only if they do not compare equal (==).

Erlang/OTP 24.0 introduced a new internal representation for sets which is more performant. Developers can use this new representation by passing the {version, 2} flag to new/1 and from_list/2, such as sets:new([{version, 2}]). This new representation will become the default in future Erlang/OTP versions. Functions that work on two sets, such as union/2 and similar, will work with sets of different versions. In such cases, there is no guarantee about the version of the returned set. Explicit conversion from the old version to the new one can be done with sets:from_list(sets:to_list(Old), [{version,2}]).

Compatibility

The following functions in this module also exist and provide the same functionality in the gb_sets(3) and ordsets(3) modules. That is, by only changing the module name for each call, you can try out different set representations.

add_element/2 del_element/2 filter/2 fold/3 from_list/1 intersection/1 intersection/2 is_element/2 is_empty/1 is_set/1 is_subset/2 new/0 size/1 subtract/2 to_list/1 union/1 union/2

While the three set implementations offer the same functionality with respect to the aforementioned functions, their overall behavior may differ. As mentioned, this module considers elements as different if and only if they do not match (=:=), while both ordsets and gb_sets consider elements as different if and only if they do not compare equal (==).

Example:

1> sets:is_element(1.0, sets:from_list([1])).
false
2> ordsets:is_element(1.0, ordsets:from_list([1])).
true
2> gb_sets:is_element(1.0, gb_sets:from_list([1])).
true

As returned by new/0.

Add an element to a Set.

Returns a new set formed from Set1 with Element inserted.

Remove an element from a Set.

Returns Set1, but with Element removed.

Filter set elements.

Filters elements in Set1 with boolean function Pred.

Fold over set elements.

Folds Function over every element in Set and returns the final value of the accumulator. The evaluation order is undefined.

Convert a list into a Set.

Returns a set of the elements in List.

Convert a list into a Set at the given version.

Returns a set of the elements in List at the given version.

Return the intersection of a list of Sets.

Returns the intersection of the non-empty list of sets.

Return the intersection of two Sets.

Returns the intersection of Set1 and Set2.

Check whether two Sets are disjoint.

Returns true if Set1 and Set2 are disjoint (have no elements in common), otherwise false.

Test for membership of a Set.

Returns true if Element is an element of Set, otherwise false.

Test for empty set.

Returns true if Set is an empty set, otherwise false.

Test for a Set.

Returns true if Set appears to be a set of elements, otherwise false. Note that the test is shallow and will return true for any term that coincides with the possible representations of a set. See also note on data types.

Test for subset.

Returns true when every element of Set1 is also a member of Set2, otherwise false.

Return an empty set.

Returns a new empty set.

Return an empty set at the given version.

Returns a new empty set at the given version.

Return the number of elements in a set.

Returns the number of elements in Set.

Return the difference of two Sets.

Returns only the elements of Set1 that are not also elements of Set2.

Convert a Setinto a list.

Returns the elements of Set as a list. The order of the returned elements is undefined.

Return the union of a list of Sets.

Returns the merged (union) set of the list of sets.

Return the union of two Sets.

Returns the merged (union) set of Set1 and Set2.