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<html xmlns="http://www.w3.org/1999/xhtml"><head><title>CCCache (containers-data.CCCache)</title><link rel="stylesheet" href="../../odoc.css"/><meta charset="utf-8"/><meta name="generator" content="odoc 2.1.0"/><meta name="viewport" content="width=device-width,initial-scale=1.0"/><script src="../../highlight.pack.js"></script><script>hljs.initHighlightingOnLoad();</script></head><body class="odoc"><nav class="odoc-nav"><a href="../index.html">Up</a> – <a href="../index.html">containers-data</a> » CCCache</nav><header class="odoc-preamble"><h1>Module <code><span>CCCache</span></code></h1><p>Caches Utils</p><p>Particularly useful for memoization. See <a href="#val-with_cache"><code>with_cache</code></a> and <a href="#val-with_cache_rec"><code>with_cache_rec</code></a> for more details.</p><ul class="at-tags"><li class="since"><span class="at-tag">since</span> 0.6</li></ul></header><nav class="odoc-toc"><ul><li><a href="#value-interface">Value interface</a></li></ul></nav><div class="odoc-content"><div class="odoc-spec"><div class="spec type" id="type-equal" class="anchored"><a href="#type-equal" class="anchor"></a><code><span><span class="keyword">type</span> <span>'a equal</span></span><span> = <span><span class="type-var">'a</span> <span class="arrow">-></span></span> <span><span class="type-var">'a</span> <span class="arrow">-></span></span> bool</span></code></div></div><div class="odoc-spec"><div class="spec type" id="type-hash" class="anchored"><a href="#type-hash" class="anchor"></a><code><span><span class="keyword">type</span> <span>'a hash</span></span><span> = <span><span class="type-var">'a</span> <span class="arrow">-></span></span> int</span></code></div></div><h3 id="value-interface"><a href="#value-interface" class="anchor"></a>Value interface</h3><p>Typical use case: one wants to memoize a function <code>f : 'a -> 'b</code>. Code sample:</p><pre><code>let f x =
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print_endline "call f";
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x + 1;;
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let f' = with_cache (lru 256) f;;
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f' 0;; (* prints *)
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f' 1;; (* prints *)
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f' 0;; (* doesn't print, returns cached value *)</code></pre><ul class="at-tags"><li class="since"><span class="at-tag">since</span> 0.6</li></ul><div class="odoc-spec"><div class="spec type" id="type-t" class="anchored"><a href="#type-t" class="anchor"></a><code><span><span class="keyword">type</span> <span>('a, 'b) t</span></span></code></div></div><div class="odoc-spec"><div class="spec value" id="val-clear" class="anchored"><a href="#val-clear" class="anchor"></a><code><span><span class="keyword">val</span> clear : <span><span><span>( <span class="type-var">_</span>, <span class="type-var">_</span> )</span> <a href="#type-t">t</a></span> <span class="arrow">-></span></span> unit</span></code></div><div class="spec-doc"><p>Clear the content of the cache.</p></div></div><div class="odoc-spec"><div class="spec type" id="type-callback" class="anchored"><a href="#type-callback" class="anchor"></a><code><span><span class="keyword">type</span> <span>('a, 'b) callback</span></span><span> = <span>in_cache:bool <span class="arrow">-></span></span> <span><span class="type-var">'a</span> <span class="arrow">-></span></span> <span><span class="type-var">'b</span> <span class="arrow">-></span></span> unit</span></code></div><div class="spec-doc"><p>Type of the callback that is called once a cached value is found or not. Should never raise.</p><ul class="at-tags"><li class="parameter"><span class="at-tag">parameter</span> <span class="value">in_cache</span> <p>is <code>true</code> if the value was in cache, <code>false</code> if the value was just produced.</p></li></ul><ul class="at-tags"><li class="since"><span class="at-tag">since</span> 1.3</li></ul></div></div><div class="odoc-spec"><div class="spec value" id="val-with_cache" class="anchored"><a href="#val-with_cache" class="anchor"></a><code><span><span class="keyword">val</span> with_cache :
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<span>?cb:<span><span>( <span class="type-var">'a</span>, <span class="type-var">'b</span> )</span> <a href="#type-callback">callback</a></span> <span class="arrow">-></span></span>
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<span><span><span>( <span class="type-var">'a</span>, <span class="type-var">'b</span> )</span> <a href="#type-t">t</a></span> <span class="arrow">-></span></span>
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<span><span>( <span><span class="type-var">'a</span> <span class="arrow">-></span></span> <span class="type-var">'b</span> )</span> <span class="arrow">-></span></span>
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<span><span class="type-var">'a</span> <span class="arrow">-></span></span>
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<span class="type-var">'b</span></span></code></div><div class="spec-doc"><p><code>with_cache c f</code> behaves like <code>f</code>, but caches calls to <code>f</code> in the cache <code>c</code>. It always returns the same value as <code>f x</code>, if <code>f x</code> returns, or raise the same exception. However, <code>f</code> may not be called if <code>x</code> is in the cache.</p><ul class="at-tags"><li class="parameter"><span class="at-tag">parameter</span> <span class="value">cb</span> <p>called after the value is generated or retrieved.</p></li></ul></div></div><div class="odoc-spec"><div class="spec value" id="val-with_cache_rec" class="anchored"><a href="#val-with_cache_rec" class="anchor"></a><code><span><span class="keyword">val</span> with_cache_rec :
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<span>?cb:<span><span>( <span class="type-var">'a</span>, <span class="type-var">'b</span> )</span> <a href="#type-callback">callback</a></span> <span class="arrow">-></span></span>
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<span><span><span>( <span class="type-var">'a</span>, <span class="type-var">'b</span> )</span> <a href="#type-t">t</a></span> <span class="arrow">-></span></span>
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<span><span>( <span><span>( <span><span class="type-var">'a</span> <span class="arrow">-></span></span> <span class="type-var">'b</span> )</span> <span class="arrow">-></span></span> <span><span class="type-var">'a</span> <span class="arrow">-></span></span> <span class="type-var">'b</span> )</span> <span class="arrow">-></span></span>
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<span><span class="type-var">'a</span> <span class="arrow">-></span></span>
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<span class="type-var">'b</span></span></code></div><div class="spec-doc"><p><code>with_cache_rec c f</code> is a function that first, applies <code>f</code> to some <code>f' = fix f</code>, such that recursive calls to <code>f'</code> are cached in <code>c</code>. It is similar to <a href="#val-with_cache"><code>with_cache</code></a> but with a function that takes as first argument its own recursive version. Example (memoized Fibonacci function):</p><pre><code>let fib = with_cache_rec (lru 256)
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(fun fib' n -> match n with
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| 1 | 2 -> 1
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| _ -> fib' (n-1) + fib' (n-2)
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);;
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fib 70;;</code></pre><ul class="at-tags"><li class="parameter"><span class="at-tag">parameter</span> <span class="value">cb</span> <p>called after the value is generated or retrieved.</p></li></ul></div></div><div class="odoc-spec"><div class="spec value" id="val-size" class="anchored"><a href="#val-size" class="anchor"></a><code><span><span class="keyword">val</span> size : <span><span><span>( <span class="type-var">_</span>, <span class="type-var">_</span> )</span> <a href="#type-t">t</a></span> <span class="arrow">-></span></span> int</span></code></div><div class="spec-doc"><p>Size of the cache (number of entries). At most linear in the number of entries.</p></div></div><div class="odoc-spec"><div class="spec value" id="val-iter" class="anchored"><a href="#val-iter" class="anchor"></a><code><span><span class="keyword">val</span> iter : <span><span><span>( <span class="type-var">'a</span>, <span class="type-var">'b</span> )</span> <a href="#type-t">t</a></span> <span class="arrow">-></span></span> <span><span>( <span><span class="type-var">'a</span> <span class="arrow">-></span></span> <span><span class="type-var">'b</span> <span class="arrow">-></span></span> unit )</span> <span class="arrow">-></span></span> unit</span></code></div><div class="spec-doc"><p>Iterate on cached values. Should yield <code>size cache</code> pairs.</p></div></div><div class="odoc-spec"><div class="spec value" id="val-add" class="anchored"><a href="#val-add" class="anchor"></a><code><span><span class="keyword">val</span> add : <span><span><span>( <span class="type-var">'a</span>, <span class="type-var">'b</span> )</span> <a href="#type-t">t</a></span> <span class="arrow">-></span></span> <span><span class="type-var">'a</span> <span class="arrow">-></span></span> <span><span class="type-var">'b</span> <span class="arrow">-></span></span> bool</span></code></div><div class="spec-doc"><p>Manually add a cached value. Return <code>true</code> if the value has successfully been added, and <code>false</code> if the value was already bound.</p><ul class="at-tags"><li class="since"><span class="at-tag">since</span> 1.5</li></ul></div></div><div class="odoc-spec"><div class="spec value" id="val-dummy" class="anchored"><a href="#val-dummy" class="anchor"></a><code><span><span class="keyword">val</span> dummy : <span><span>( <span class="type-var">'a</span>, <span class="type-var">'b</span> )</span> <a href="#type-t">t</a></span></span></code></div><div class="spec-doc"><p>Dummy cache, never stores any value.</p></div></div><div class="odoc-spec"><div class="spec value" id="val-linear" class="anchored"><a href="#val-linear" class="anchor"></a><code><span><span class="keyword">val</span> linear : <span>eq:<span><span class="type-var">'a</span> <a href="#type-equal">equal</a></span> <span class="arrow">-></span></span> <span>int <span class="arrow">-></span></span> <span><span>( <span class="type-var">'a</span>, <span class="type-var">'b</span> )</span> <a href="#type-t">t</a></span></span></code></div><div class="spec-doc"><p>Linear cache with the given size. It stores key/value pairs in an array and does linear search at every call, so it should only be used with small size.</p><ul class="at-tags"><li class="parameter"><span class="at-tag">parameter</span> <span class="value">eq</span> <p>optional equality predicate for keys.</p></li></ul></div></div><div class="odoc-spec"><div class="spec value" id="val-replacing" class="anchored"><a href="#val-replacing" class="anchor"></a><code><span><span class="keyword">val</span> replacing : <span>eq:<span><span class="type-var">'a</span> <a href="#type-equal">equal</a></span> <span class="arrow">-></span></span> <span>?hash:<span><span class="type-var">'a</span> <a href="#type-hash">hash</a></span> <span class="arrow">-></span></span> <span>int <span class="arrow">-></span></span> <span><span>( <span class="type-var">'a</span>, <span class="type-var">'b</span> )</span> <a href="#type-t">t</a></span></span></code></div><div class="spec-doc"><p>Replacing cache of the given size. Equality and hash functions can be parametrized. It's a hash table that handles collisions by replacing the old value with the new (so a cache entry is evicted when another entry with the same hash (modulo size) is added). Never grows wider than the given size.</p></div></div><div class="odoc-spec"><div class="spec value" id="val-lru" class="anchored"><a href="#val-lru" class="anchor"></a><code><span><span class="keyword">val</span> lru : <span>eq:<span><span class="type-var">'a</span> <a href="#type-equal">equal</a></span> <span class="arrow">-></span></span> <span>?hash:<span><span class="type-var">'a</span> <a href="#type-hash">hash</a></span> <span class="arrow">-></span></span> <span>int <span class="arrow">-></span></span> <span><span>( <span class="type-var">'a</span>, <span class="type-var">'b</span> )</span> <a href="#type-t">t</a></span></span></code></div><div class="spec-doc"><p>LRU cache of the given size ("Least Recently Used": keys that have not been used recently are deleted first). Never grows wider than the given size.</p></div></div><div class="odoc-spec"><div class="spec value" id="val-unbounded" class="anchored"><a href="#val-unbounded" class="anchor"></a><code><span><span class="keyword">val</span> unbounded : <span>eq:<span><span class="type-var">'a</span> <a href="#type-equal">equal</a></span> <span class="arrow">-></span></span> <span>?hash:<span><span class="type-var">'a</span> <a href="#type-hash">hash</a></span> <span class="arrow">-></span></span> <span>int <span class="arrow">-></span></span> <span><span>( <span class="type-var">'a</span>, <span class="type-var">'b</span> )</span> <a href="#type-t">t</a></span></span></code></div><div class="spec-doc"><p>Unbounded cache, backed by a Hash table. Will grow forever unless <a href="#val-clear"><code>clear</code></a> is called manually.</p></div></div></div></body></html> |