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<link title="Extlib" rel="Chapter" href="Extlib.html"><title>Batteries user guide : BatCache</title>
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<h1>Module <a href="type_BatCache.html">BatCache</a></h1>
<pre><span class="keyword">module</span> BatCache: <code class="code"><span class="keyword">sig</span></code> <a href="BatCache.html">..</a> <code class="code"><span class="keyword">end</span></code></pre><div class="info module top">
The data structure for a manual cache with keys <code class="code"><span class="keywordsign">'</span>a</code> and values <code class="code"><span class="keywordsign">'</span>b</code>.
<p>
This cache gives access to some internals of a memoized function
<code class="code">f</code>, called the generating function. This function is usually
pure; always returning the same output for a given input. This
module allows the results of complex functions to be cached so
that the function does not need to be called again to get that
result.
<p>
When <code class="code">c.get k</code> is called, an internal structure is first consulted to
see if <code class="code">f k</code> has been stored in that structure. If it has, then
that previous result is returned, otherwise, <code class="code">f k</code> is evaluated,
the result stored in the caching structure and also returned to
the user.
<p>
The user is allowed to remove a value from the caching structure
with <code class="code">c.del k</code>. This allows the user to prevent unbounded growth
of the cache by removing unneeded entries. If the user prefers an
automatically managed cache, this module provides <code class="code">!auto_cache</code>.
<p>
Last, <code class="code">c.enum ()</code> will enumerate all the currently memorized
bindings as pairs. This allows inspection of what is currently
cached.<br>
</div>
<hr width="100%">
<pre><code><span id="TYPEmanual_cache"><span class="keyword">type</span> <code class="type">('a, 'b)</code> manual_cache</span> = {</code></pre><table class="typetable">
<tr>
<td align="left" valign="top" >
<code> </code></td>
<td align="left" valign="top" >
<code><span id="TYPEELTmanual_cache.get">get</span> : <code class="type">'a -> 'b</code>;</code></td>
</tr>
<tr>
<td align="left" valign="top" >
<code> </code></td>
<td align="left" valign="top" >
<code><span id="TYPEELTmanual_cache.del">del</span> : <code class="type">'a -> unit</code>;</code></td>
</tr>
<tr>
<td align="left" valign="top" >
<code> </code></td>
<td align="left" valign="top" >
<code><span id="TYPEELTmanual_cache.enum">enum</span> : <code class="type">unit -> ('a * 'b) <a href="BatEnum.html#TYPEt">BatEnum.t</a></code>;</code></td>
</tr></table>
}
<pre><span id="VALmake_ht"><span class="keyword">val</span> make_ht</span> : <code class="type">gen:('a -> 'b) -> init_size:int -> ('a, 'b) <a href="BatCache.html#TYPEmanual_cache">manual_cache</a></code></pre><div class="info ">
Make a manual cache backed by a hashtable. The generating
function is passed with <code class="code">~gen</code> and the initial size of the
hashtable is <code class="code">~init_size</code>. The hashtable uses the polymorphic
<code class="code">hash</code> and <code class="code">(=)</code>.<br>
</div>
<pre><span id="VALmake_map"><span class="keyword">val</span> make_map</span> : <code class="type">gen:('a -> 'b) -> ('a, 'b) <a href="BatCache.html#TYPEmanual_cache">manual_cache</a></code></pre><div class="info ">
Make a manual cache for function <code class="code">~gen</code> backed by a Set.t. This
set uses the polymorphic <code class="code">(<)</code> for comparison, so <code class="code"><span class="keywordsign">'</span>a</code> should be
properly comparable by it.<br>
</div>
<pre><span id="TYPEauto_cache"><span class="keyword">type</span> <code class="type">('a, 'b)</code> auto_cache</span> = <code class="type">'a -> 'b</code> </pre>
<div class="info ">
Automatically managed caches
<p>
This type of cache is more transparent than the <code class="code">!manual_cache</code>
above. It does not provide inspection of the caching structure,
but guarantees bounded memory usage through some policy of
discarding some entries.
<p>
Each auto-cache can have a different policy to decide which entry
to discard.<br>
</div>
<pre><span id="VALlru_cache"><span class="keyword">val</span> lru_cache</span> : <code class="type">gen:('a -> 'b) -> cap:int -> ('a, 'b) <a href="BatCache.html#TYPEauto_cache">auto_cache</a></code></pre></body></html>
