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<head><title>cacheValue -- cache values of functions in their arguments</title>
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<div><h1>cacheValue -- cache values of functions in their arguments</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>((cacheValue KEY) f) x</tt></div>
</dd></dl>
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</li>
<li><div class="single">Inputs:<ul><li><span><tt>KEY</tt></span></li>
<li><span><tt>f</tt>, <span>a <a href="___Function.html">function</a></span></span></li>
<li><span><tt>x</tt>, an argument for <tt>f</tt> that has <span>a <a href="___Cache__Table.html">cache table</a></span> stored in it under <tt>x.cache</tt></span></li>
</ul>
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</li>
<li><div class="single">Outputs:<ul><li><span><tt>f x</tt> is returned, but the value is saved in <tt>x.cache#KEY</tt> and not recomputed later. However, if the value found in <tt>x.cache#KEY</tt> is <span>an <a href="___Cache__Function.html">a cache function</a></span>, such as is returned by <tt>(stashValue KEY) f</tt>, then the value of <tt>x.cache#KEY x</tt> is returned instead, after first removing <tt>x.cache#KEY</tt> from <tt>x.cache</tt>.</span></li>
</ul>
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<div class="single"><h2>Description</h2>
<div><table class="examples"><tr><td><pre>i1 : x = new HashTable from { val => 1000, cache => new CacheTable }
o1 = HashTable{cache => CacheTable{}}
val => 1000
o1 : HashTable</pre>
</td></tr>
<tr><td><pre>i2 : f = (t -> (print "hi there"; t.val^4))
o2 = f
o2 : FunctionClosure</pre>
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<tr><td><pre>i3 : h = (cacheValue VALUE) f
o3 = {*a cache function*}
o3 : CacheFunction</pre>
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<tr><td><pre>i4 : h x
hi there
o4 = 1000000000000</pre>
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<tr><td><pre>i5 : h x
o5 = 1000000000000</pre>
</td></tr>
<tr><td><pre>i6 : peek'_2 x
o6 = HashTable{cache => CacheTable{VALUE => 1000000000000}}
val => 1000</pre>
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<div class="single"><h2>See also</h2>
<ul><li><span><a href="_stash__Value.html" title="stash values of functions in their arguments">stashValue</a> -- stash values of functions in their arguments</span></li>
</ul>
</div>
<div class="waystouse"><div class="single"><h2>Code</h2>
<pre>../../m2/methods.m2:506:18-515:26: --source code:
cacheValue = key -> f -> new CacheFunction from (x -> (
c := try x.cache else x.cache = new CacheTable;
if c#?key then (
val := c#key;
if class val === CacheFunction then (
remove(c,key);
c#key = val x)
else val
)
else c#key = f x))</pre>
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