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<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE erlref SYSTEM "erlref.dtd">

<erlref>
  <header>
    <copyright>
      <year>2000</year><year>2015</year>
      <holder>Ericsson AB. All Rights Reserved.</holder>
    </copyright>
    <legalnotice>
      The contents of this file are subject to the Erlang Public License,
      Version 1.1, (the "License"); you may not use this file except in
      compliance with the License. You should have received a copy of the
      Erlang Public License along with this software. If not, it can be
      retrieved online at http://www.erlang.org/.
    
      Software distributed under the License is distributed on an "AS IS"
      basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
      the License for the specific language governing rights and limitations
      under the License.
    
    </legalnotice>

    <title>sets</title>
    <prepared>Robert Virding</prepared>
    <responsible>Bjarne Dacker</responsible>
    <docno>1</docno>
    <approved>Bjarne D&auml;cker</approved>
    <checked></checked>
    <date>99-07-27</date>
    <rev>A</rev>
    <file>sets.sgml</file>
  </header>
  <module>sets</module>
  <modulesummary>Functions for Set Manipulation</modulesummary>
  <description>
    <p>Sets are collections of elements with no duplicate elements.
      The representation of a set is not defined.</p>
    <p>This module provides exactly the same interface as the module
      <c>ordsets</c> but with a defined representation. One difference is
      that while this module considers two elements as different if they
      do not match (<c>=:=</c>), <c>ordsets</c> considers two elements as
      different if and only if they do not compare equal (<c>==</c>).</p>
  </description>

  <datatypes>
    <datatype>
      <name name="set" n_vars="1"/>
      <desc><p>As returned by <c>new/0</c>.</p></desc>
    </datatype>
    <datatype>
      <name name="set" n_vars="0"/>
    </datatype>
  </datatypes>
  <funcs>
    <func>
      <name name="new" arity="0"/>
      <fsummary>Return an empty set</fsummary>
      <desc>
        <p>Returns a new empty set.</p>
      </desc>
    </func>
    <func>
      <name name="is_set" arity="1"/>
      <fsummary>Test for a <c>Set</c></fsummary>
      <desc>
        <p>Returns <c>true</c> if <c><anno>Set</anno></c> is a set of
          elements, otherwise <c>false</c>.</p>
      </desc>
    </func>
    <func>
      <name name="size" arity="1"/>
      <fsummary>Return the number of elements in a set</fsummary>
      <desc>
        <p>Returns the number of elements in <c><anno>Set</anno></c>.</p>
      </desc>
    </func>
    <func>
      <name name="to_list" arity="1"/>
      <fsummary>Convert a <c>Set</c>into a list</fsummary>
      <desc>
        <p>Returns the elements of <c><anno>Set</anno></c> as a list.
          The order of the returned elements is undefined.</p>
      </desc>
    </func>
    <func>
      <name name="from_list" arity="1"/>
      <fsummary>Convert a list into a <c>Set</c></fsummary>
      <desc>
        <p>Returns a set of the elements in <c><anno>List</anno></c>.</p>
      </desc>
    </func>
    <func>
      <name name="is_element" arity="2"/>
      <fsummary>Test for membership of a <c>Set</c></fsummary>
      <desc>
        <p>Returns <c>true</c> if <c><anno>Element</anno></c> is an element of
          <c><anno>Set</anno></c>, otherwise <c>false</c>.</p>
      </desc>
    </func>
    <func>
      <name name="add_element" arity="2"/>
      <fsummary>Add an element to a <c>Set</c></fsummary>
      <desc>
        <p>Returns a new set formed from <c><anno>Set1</anno></c> with
          <c><anno>Element</anno></c> inserted.</p>
      </desc>
    </func>
    <func>
      <name name="del_element" arity="2"/>
      <fsummary>Remove an element from a <c>Set</c></fsummary>
      <desc>
        <p>Returns <c><anno>Set1</anno></c>, but with <c><anno>Element</anno></c> removed.</p>
      </desc>
    </func>
    <func>
      <name name="union" arity="2"/>
      <fsummary>Return the union of two <c>Sets</c></fsummary>
      <desc>
        <p>Returns the merged (union) set of <c><anno>Set1</anno></c> and
          <c><anno>Set2</anno></c>.</p>
      </desc>
    </func>
    <func>
      <name name="union" arity="1"/>
      <fsummary>Return the union of a list of <c>Sets</c></fsummary>
      <desc>
        <p>Returns the merged (union) set of the list of sets.</p>
      </desc>
    </func>
    <func>
      <name name="intersection" arity="2"/>
      <fsummary>Return the intersection of two <c>Sets</c></fsummary>
      <desc>
        <p>Returns the intersection of <c><anno>Set1</anno></c> and
          <c><anno>Set2</anno></c>.</p>
      </desc>
    </func>
    <func>
      <name name="intersection" arity="1"/>
      <fsummary>Return the intersection of a list of <c>Sets</c></fsummary>
      <desc>
        <p>Returns the intersection of the non-empty list of sets.</p>
      </desc>
    </func>
    <func>
      <name name="is_disjoint" arity="2"/>
      <fsummary>Check whether two <c>Sets</c> are disjoint</fsummary>
      <desc>
        <p>Returns <c>true</c> if <c><anno>Set1</anno></c> and
          <c><anno>Set2</anno></c> are disjoint (have no elements in common),
	  and <c>false</c> otherwise.</p>
      </desc>
    </func>
    <func>
      <name name="subtract" arity="2"/>
      <fsummary>Return the difference of two <c>Sets</c></fsummary>
      <desc>
        <p>Returns only the elements of <c><anno>Set1</anno></c> which are not
          also elements of <c><anno>Set2</anno></c>.</p>
      </desc>
    </func>
    <func>
      <name name="is_subset" arity="2"/>
      <fsummary>Test for subset</fsummary>
      <desc>
        <p>Returns <c>true</c> when every element of <c><anno>Set1</anno></c>1 is
          also a member of <c><anno>Set2</anno></c>, otherwise <c>false</c>.</p>
      </desc>
    </func>
    <func>
      <name name="fold" arity="3"/>
      <fsummary>Fold over set elements</fsummary>
      <desc>
        <p>Fold <c><anno>Function</anno></c> over every element in <c><anno>Set</anno></c>
          returning the final value of the accumulator.
          The evaluation order is undefined.</p>
      </desc>
    </func>
    <func>
      <name name="filter" arity="2"/>
      <fsummary>Filter set elements</fsummary>
      <desc>
        <p>Filter elements in <c><anno>Set1</anno></c> with boolean function
          <c><anno>Pred</anno></c>.</p>
      </desc>
    </func>
  </funcs>

  <section>
    <title>See Also</title>
    <p><seealso marker="ordsets">ordsets(3)</seealso>,
      <seealso marker="gb_sets">gb_sets(3)</seealso></p>
  </section>
</erlref>