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<head><title>applyKeys -- apply a function to each key in a hash table</title>
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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="_apply__Keys.html" title="apply a function to each key in a hash table">applyKeys</a></div>
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<div><h1>applyKeys -- apply a function to each key in a hash table</h1>
<div class="single"><h2>Synopsis</h2>
<ul><li><div class="list"><dl class="element"><dt class="heading">Usage: </dt><dd class="value"><div><tt>applyKeys(H,f)</tt></div>
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<li><div class="single">Inputs:<ul><li><span><tt>H</tt>, <span>a <a href="___Hash__Table.html">hash table</a></span></span></li>
<li><span><tt>f</tt>, <span>a <a href="___Function.html">function</a></span>, with one argument</span></li>
</ul>
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<li><div class="single">Outputs:<ul><li><span><span>a <a href="___Hash__Table.html">hash table</a></span>, obtained by applying <tt>f</tt> to each key <tt>k</tt> in <tt>H</tt></span></li>
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<div class="single"><h2>Description</h2>
<div><table class="examples"><tr><td><pre>i1 : H = new HashTable from {1 => a, 2 => b, 3 => c}
o1 = HashTable{1 => a}
2 => b
3 => c
o1 : HashTable</pre>
</td></tr>
<tr><td><pre>i2 : applyKeys(H, k -> k + 100)
o2 = HashTable{101 => a}
102 => b
103 => c
o2 : HashTable</pre>
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<div class="single"><h2>Caveat</h2>
<div>It is an error for the function <tt>f</tt> to return two pairs with the same key.</div>
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<div class="single"><h2>See also</h2>
<ul><li><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></li>
<li><span><a href="_apply__Values.html" title="apply a function to each value">applyValues</a> -- apply a function to each value</span></li>
<li><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></li>
</ul>
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<div class="waystouse"><h2>Ways to use <tt>applyKeys</tt> :</h2>
<ul><li>applyKeys(HashTable,Function)</li>
</ul>
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