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<p><a id="X80589F287F1620B2" name="X80589F287F1620B2"></a></p>
<div class="ChapSects"><a href="chap8.html#X80589F287F1620B2">8 <span class="Heading">Hashsets</span></a>
<div class="ContSect"><span class="tocline"><span class="nocss"> </span><a href="chap8.html#X7C5F33687C53BEF0">8.1 <span class="Heading">API</span></a>
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<span class="ContSS"><br /><span class="nocss">  </span><a href="chap8.html#X81FA1C7B84314DAF">8.1-1 IsHashSet</a></span>
<span class="ContSS"><br /><span class="nocss">  </span><a href="chap8.html#X789A593B7C227BE5">8.1-2 HashSet</a></span>
<span class="ContSS"><br /><span class="nocss">  </span><a href="chap8.html#X7C7FBBE27E833BB3">8.1-3 AddSet</a></span>
<span class="ContSS"><br /><span class="nocss">  </span><a href="chap8.html#X7CECEB107D9B8645"><code>8.1-4 \in</code></a></span>
<span class="ContSS"><br /><span class="nocss">  </span><a href="chap8.html#X80E770C2845B4155">8.1-5 RemoveSet</a></span>
<span class="ContSS"><br /><span class="nocss">  </span><a href="chap8.html#X82596CD77B2EC7C5">8.1-6 Size</a></span>
<span class="ContSS"><br /><span class="nocss">  </span><a href="chap8.html#X8142E775878A1A6E">8.1-7 IsEmpty</a></span>
<span class="ContSS"><br /><span class="nocss">  </span><a href="chap8.html#X7D1EE80687CAB426">8.1-8 Set</a></span>
<span class="ContSS"><br /><span class="nocss">  </span><a href="chap8.html#X835176CB8124AF70">8.1-9 AsSet</a></span>
<span class="ContSS"><br /><span class="nocss">  </span><a href="chap8.html#X792F44027D8C73DA">8.1-10 Iterator</a></span>
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<h3>8 <span class="Heading">Hashsets</span></h3>

<p>A hash set stores objects and allows efficient lookup whether an object is already a member of the set.</p>

<p><strong class="pkg">datastructures</strong> currently provides a reference implementation of hashsets using a hashtable stored in a plain <strong class="pkg">GAP</strong> list.</p>

<p><a id="X7C5F33687C53BEF0" name="X7C5F33687C53BEF0"></a></p>

<h4>8.1 <span class="Heading">API</span></h4>

<p><a id="X81FA1C7B84314DAF" name="X81FA1C7B84314DAF"></a></p>

<h5>8.1-1 IsHashSet</h5>

<div class="func"><table class="func" width="100%"><tr><td class="tdleft"><code class="func">&#an style='color: green'>8227; IsHashSet</code>( <var class="Arg">arg</var> )</td><td class="tdright">( filter )</td></tr></table></div>
<p>Returns: <code class="keyw">true</code> or <code class="keyw">false</code></p>

<p>Category of hashsets</p>

<p><a id="X789A593B7C227BE5" name="X789A593B7C227BE5"></a></p>

<h5>8.1-2 HashSet</h5>

<div class="func"><table class="func" width="100%"><tr><td class="tdleft"><code class="func">&#an style='color: green'>8227; HashSet</code>( [<var class="Arg">values</var>][,] [<var class="Arg">hashfunc</var>[, <var class="Arg">eqfunc</var>]][,] [<var class="Arg">capacity</var>] )</td><td class="tdright">( function )</td></tr></table></div>
<p>Create a new hashset. The optional argument <var class="Arg">values</var> must be a list of values, which will be inserted into the new hashset in order. The optional argument <var class="Arg">hashfunc</var> must be a hash- function, <var class="Arg">eqfunc</var> must be a binary equality testing function that returns <code class="keyw">true</code> if the two arguments are considered equal, and <code class="keyw">false</code> if they are not. Refer to Chapter <a href="chap6.html#X7AE36B967EB1382B"><span class="RefLink">6</span></a> about the requirements for hashfunctions and equality testers. The optional argument <var class="Arg">capacity</var> determines the initial size of the hashmap.</p>

<p><a id="X7C7FBBE27E833BB3" name="X7C7FBBE27E833BB3"></a></p>

<h5>8.1-3 AddSet</h5>

<div class="func"><table class="func" width="100%"><tr><td class="tdleft"><code class="func">&#an style='color: green'>8227; AddSet</code>( <var class="Arg">hashset</var>, <var class="Arg">obj</var> )</td><td class="tdright">( operation )</td></tr></table></div>
<p>Add <var class="Arg">obj</var> to <var class="Arg">hashset</var>.</p>

<p><a id="X7CECEB107D9B8645" name="X7CECEB107D9B8645"></a></p>

<h5><code>8.1-4 \in</code></h5>

<div class="func"><table class="func" width="100%"><tr><td class="tdleft"><code class="func">&#an style='color: green'>8227; \in</code>( <var class="Arg">obj</var>, <var class="Arg">hashset</var> )</td><td class="tdright">( operation )</td></tr></table></div>
<p>Test membership of <var class="Arg">obj</var> in <var class="Arg">hashset</var></p>

<p><a id="X80E770C2845B4155" name="X80E770C2845B4155"></a></p>

<h5>8.1-5 RemoveSet</h5>

<div class="func"><table class="func" width="100%"><tr><td class="tdleft"><code class="func">&#an style='color: green'>8227; RemoveSet</code>( <var class="Arg">hashset</var>, <var class="Arg">obj</var> )</td><td class="tdright">( operation )</td></tr></table></div>
<p>Remove <var class="Arg">obj</var> from <var class="Arg">hashset</var>.</p>

<p><a id="X82596CD77B2EC7C5" name="X82596CD77B2EC7C5"></a></p>

<h5>8.1-6 Size</h5>

<div class="func"><table class="func" width="100%"><tr><td class="tdleft"><code class="func">&#an style='color: green'>8227; Size</code>( <var class="Arg">hashset</var> )</td><td class="tdright">( operation )</td></tr></table></div>
<p>Return the size of a hashset Returns an integer</p>

<p><a id="X8142E775878A1A6E" name="X8142E775878A1A6E"></a></p>

<h5>8.1-7 IsEmpty</h5>

<div class="func"><table class="func" width="100%"><tr><td class="tdleft"><code class="func">&#an style='color: green'>8227; IsEmpty</code>( <var class="Arg">hashset</var> )</td><td class="tdright">( operation )</td></tr></table></div>
<p>Returns: a boolean</p>

<p>Test a hashset for emptiness.</p>

<p><a id="X7D1EE80687CAB426" name="X7D1EE80687CAB426"></a></p>

<h5>8.1-8 Set</h5>

<div class="func"><table class="func" width="100%"><tr><td class="tdleft"><code class="func">&#an style='color: green'>8227; Set</code>( <var class="Arg">hashset</var> )</td><td class="tdright">( operation )</td></tr></table></div>
<p>Returns: a set</p>

<p>Convert a hashset into a <strong class="pkg">GAP</strong> set</p>

<p><a id="X835176CB8124AF70" name="X835176CB8124AF70"></a></p>

<h5>8.1-9 AsSet</h5>

<div class="func"><table class="func" width="100%"><tr><td class="tdleft"><code class="func">&#an style='color: green'>8227; AsSet</code>( <var class="Arg">hashset</var> )</td><td class="tdright">( operation )</td></tr></table></div>
<p>Returns: an immutable set</p>

<p>Convert a hashset into a <strong class="pkg">GAP</strong> set</p>

<p><a id="X792F44027D8C73DA" name="X792F44027D8C73DA"></a></p>

<h5>8.1-10 Iterator</h5>

<div class="func"><table class="func" width="100%"><tr><td class="tdleft"><code class="func">&#an style='color: green'>8227; Iterator</code>( <var class="Arg">set</var> )</td><td class="tdright">( operation )</td></tr></table></div>
<p>Returns: an iterator</p>

<p>Create an iterator for the values contained in a hashset. Note that elements added to the hashset after the creation of an iterator are not guaranteed to be returned by that iterator.</p>


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