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<div><a href="index.html" title="">Macaulay2Doc</a> > <a href="___The_sp__Macaulay2_splanguage.html" title="">The Macaulay2 language</a> > <a href="_hash_sptables.html" title="">hash tables</a> > <a href="___Hash__Table.html" title="the class of all hash tables">HashTable</a></div>
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<div><h1>HashTable -- the class of all hash tables</h1>
<div class="single"><h2>Description</h2>
<div><p>A hash table consists of: a class type, a parent type, and a set of key-value pairs. The keys and values can be anything. The access functions below accept a key and return the corresponding value. For details of the mechanism underlying this, see <a href="_hashing.html" title="">hashing</a>.</p>
<p>One important feature of hash tables that when the keys are consecutive integers starting at 0, the keys are scanned in the natural order.</p>
<p>There is a subclass of HashTable called <a href="___Mutable__Hash__Table.html" title="the class of all mutable hash tables">MutableHashTable</a> which consists of those hash tables whose entries can be changed.</p>
<p>Access functions:</p>
<ul><li><span><a href="__sh.html" title="length, or access to elements">#</a> -- length, or access to elements</span></li>
<li><span><a href="_..html" title="access to elements whose key is a symbol">.</a> -- access to elements whose key is a symbol</span></li>
</ul>
<p>Query functions:</p>
<ul><li><span><a href="__sh_qu.html" title="check for presence of elements">#?</a> -- check for presence of elements</span></li>
<li><span><a href="_._qu.html" title="check for presence of elements whose key is a symbol">.?</a> -- check for presence of elements whose key is a symbol</span></li>
</ul>
</div>
</div>
<div class="waystouse"><h2>Types of hash table :</h2>
<ul><li><span><a href="___Coherent__Sheaf.html" title="the class of all coherent sheaves">CoherentSheaf</a> -- the class of all coherent sheaves</span></li>
<li><span><a href="___Ideal.html" title="the class of all ideals">Ideal</a> -- the class of all ideals</span></li>
<li><span><a href="___Immutable__Type.html" title="the class of immutable types">ImmutableType</a> -- the class of immutable types</span></li>
<li><span><a href="___Module__Map.html" title="the class of all maps between modules">ModuleMap</a> -- the class of all maps between modules</span></li>
<li><span><a href="___Monoid__Element.html" title="the class of all monoid elements">MonoidElement</a> -- the class of all monoid elements</span></li>
<li><span><a href="___Mutable__Hash__Table.html" title="the class of all mutable hash tables">MutableHashTable</a> -- the class of all mutable hash tables</span></li>
<li><span><a href="___Mutable__Matrix.html" title="the class of all mutable matrices">MutableMatrix</a> -- the class of all mutable matrices</span></li>
<li><span><a href="___Option__Table.html" title="the class of hash tables for optional arguments">OptionTable</a> -- the class of hash tables for optional arguments</span></li>
<li><span><a href="___Projective__Hilbert__Polynomial.html" title="the class of all Hilbert polynomials">ProjectiveHilbertPolynomial</a> -- the class of all Hilbert polynomials</span></li>
<li><span><a href="___Ring__Map.html" title="the class of all ring maps">RingMap</a> -- the class of all ring maps</span></li>
<li><span><a href="___Sheaf__Of__Rings.html" title="the class of sheaves of rings">SheafOfRings</a> -- the class of sheaves of rings</span></li>
<li><span><a href="___Tally.html" title="the class of all tally results">Tally</a> -- the class of all tally results</span></li>
</ul>
<h2>Functions and methods returning a hash table :</h2>
<ul><li><span>applyKeys(HashTable,Function), see <span><a href="_apply__Keys.html" title="apply a function to each key in a hash table">applyKeys</a> -- apply a function to each key in a hash table</span></span></li>
<li><span>applyPairs(HashTable,Function), see <span><a href="_apply__Pairs.html" title="apply a function to each pair in a hash table">applyPairs</a> -- apply a function to each pair in a hash table</span></span></li>
<li><span>applyValues(HashTable,Function), see <span><a href="_apply__Values.html" title="apply a function to each value">applyValues</a> -- apply a function to each value</span></span></li>
<li><span>hashTable(List), see <span><a href="_hash__Table.html" title="make a hash table">hashTable</a> -- make a hash table</span></span></li>
<li><span><a href="_instances_lp__Type_rp.html" title="">instances(Type)</a></span></li>
<li><span><a href="_merge_lp__Hash__Table_cm__Hash__Table_cm__Function_rp.html" title="merge hash tables">merge(HashTable,HashTable,Function)</a> -- merge hash tables</span></li>
<li><span><a href="_new_sp__Hash__Table_spfrom_sp__List.html" title="make a hash table from a list">new HashTable from List</a> -- make a hash table from a list</span></li>
<li><span><a href="_select_lp__Hash__Table_cm__Function_rp.html" title="select part of a hash table">select(HashTable,Function)</a> -- select part of a hash table</span></li>
<li><span><a href="_select_lp__Z__Z_cm__Hash__Table_cm__Function_rp.html" title="select a limited number of pairs from a hash table">select(ZZ,HashTable,Function)</a> -- select a limited number of pairs from a hash table</span></li>
</ul>
<h2>Methods that use a hash table :</h2>
<ul><li><span><a href="__sh_sp__Hash__Table.html" title="length"># HashTable</a> -- length</span></li>
<li><span><a href="_add__Hook_lp__Hash__Table_cm__Thing_cm__Function_rp.html" title="add a hook function to an object for later processing">addHook(HashTable,Thing,Function)</a> -- add a hook function to an object for later processing</span></li>
<li><span><a href="_all_lp__Hash__Table_cm__Function_rp.html" title="whether all key/value pairs in a hash table satisfy a specified condition">all(HashTable,Function)</a> -- whether all key/value pairs in a hash table satisfy a specified condition</span></li>
<li><span><a href="_any_lp__Hash__Table_cm__Function_rp.html" title="whether all key/value pairs in a hash table satisfy a specified condition">any(HashTable,Function)</a> -- whether all key/value pairs in a hash table satisfy a specified condition</span></li>
<li><span><a href="___Hash__Table_sp_sh_sp__Thing.html" title="get value from hash table">HashTable # Thing</a> -- get value from hash table</span></li>
<li><span><a href="___Hash__Table_sp_sh_qu_sp__Thing.html" title="check for value in hash table">HashTable #? Thing</a> -- check for value in hash table</span></li>
<li><span><a href="_indices_lp__Hash__Table_rp.html" title="preferred indices of a direct sum">indices(HashTable)</a> -- preferred indices of a direct sum</span></li>
<li><span>installAssignmentMethod(Symbol,HashTable,Function), see <span><a href="_install__Assignment__Method.html" title="install methods assignment to the value of an operator">installAssignmentMethod</a> -- install methods assignment to the value of an operator</span></span></li>
<li><span>installAssignmentMethod(Symbol,HashTable,HashTable,Function), see <span><a href="_install__Assignment__Method.html" title="install methods assignment to the value of an operator">installAssignmentMethod</a> -- install methods assignment to the value of an operator</span></span></li>
<li><span>installAssignmentMethod(Symbol,HashTable,HashTable,Option), see <span><a href="_install__Assignment__Method.html" title="install methods assignment to the value of an operator">installAssignmentMethod</a> -- install methods assignment to the value of an operator</span></span></li>
<li><span>installAssignmentMethod(Symbol,HashTable,Option), see <span><a href="_install__Assignment__Method.html" title="install methods assignment to the value of an operator">installAssignmentMethod</a> -- install methods assignment to the value of an operator</span></span></li>
<li><span><a href="_keys_lp__Hash__Table_rp.html" title="keys used in a hash table">keys(HashTable)</a> -- keys used in a hash table</span></li>
<li><span>package(HashTable), see <span><a href="_package.html" title="get containing package">package</a> -- get containing package</span></span></li>
<li><span>pairs(HashTable), see <span><a href="_pairs.html" title="list the pairs in a hash table">pairs</a> -- list the pairs in a hash table</span></span></li>
<li><span>remove(HashTable,Thing), see <span><a href="_remove.html" title="remove an entry from a hash table">remove</a> -- remove an entry from a hash table</span></span></li>
<li><span><a href="_remove__Hook_lp__Hash__Table_cm__Thing_cm__Function_rp.html" title="remove a hook function from an object">removeHook(HashTable,Thing,Function)</a> -- remove a hook function from an object</span></li>
<li><span><a href="_run__Hooks_lp__Hash__Table_cm__Thing_cm__Thing_rp.html" title="run the hook functions stored in an object">runHooks(HashTable,Thing,Thing)</a> -- run the hook functions stored in an object</span></li>
<li><span>scanKeys(HashTable,Function), see <span><a href="_scan__Keys.html" title="apply a function to each key in a hash table or database">scanKeys</a> -- apply a function to each key in a hash table or database</span></span></li>
<li><span><a href="_scan__Pairs_lp__Hash__Table_cm__Function_rp.html" title="apply a function to pairs in a hash table">scanPairs(HashTable,Function)</a> -- apply a function to pairs in a hash table</span></li>
<li><span>scanValues(HashTable,Function), see <span><a href="_scan__Values.html" title="apply a function to each value in a hash table">scanValues</a> -- apply a function to each value in a hash table</span></span></li>
<li><span><a href="_values_lp__Hash__Table_rp.html" title="values in a hash table">values(HashTable)</a> -- values in a hash table</span></li>
</ul>
<h2>Fixed objects of class HashTable :</h2>
<ul><li><span>Layout, see <span><a href="_current__Layout.html" title="relative locations of Macaulay2 files">currentLayout</a> -- relative locations of Macaulay2 files</span></span></li>
<li><span><a href="_operator__Attributes.html" title="">operatorAttributes</a></span></li>
<li><span><a href="_version.html" title="information about this version of the program">version</a> -- information about this version of the program</span></li>
</ul>
</div>
<div class="waystouse"><h2>For the programmer</h2>
<p>The object <a href="___Hash__Table.html" title="the class of all hash tables">HashTable</a> is <span>a <a href="___Type.html">type</a></span>, with ancestor class <a href="___Thing.html" title="the class of all things">Thing</a>.</p>
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