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POWhat are some other languages that support "partial specialization"?
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  1. POWhat are some other languages that support "partial specialization"?
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    copied!<p>Partial template specialization is one of the most important concepts for generic programming in C++. For example: to implement a generic swap function:</p> <pre><code>template &lt;typename T&gt; void swap(T &amp;x, T &amp;y) { const T tmp = x; y = x; x = tmp; } </code></pre> <p>To specialize it for a vector to support O(1) swap:</p> <pre><code>template &lt;typename T, class Alloc&gt; void swap(vector&lt;T, Alloc&gt; &amp;x, vector&lt;T, Alloc&gt; &amp;y) { x.swap(y); } </code></pre> <p>So you can always get optimal performance when you call swap(x, y) in a generic function;</p> <p>Much appreciated, if you can post the equivalent (or the canonical example of partial specialization of the language if the language doesn't support the swap concept) in alternative languages.</p> <p><strong>EDIT</strong>: so it looks like many people who answered/commented really don't known what partial specialization is, and that the generic swap example seems to get in the way of understanding by some people. A more general example would be:</p> <pre><code>template &lt;typename T&gt; void foo(T x) { generic_foo(x); } </code></pre> <p>A partial specialization would be:</p> <pre><code>template &lt;typename T&gt; void foo(vector&lt;T&gt; x) { partially_specialized_algo_for_vector(x); } </code></pre> <p>A complete specialization would be:</p> <pre><code>void foo(vector&lt;bool&gt; bitmap) { special_algo_for_bitmap(bitmap); } </code></pre> <p>Why this is important? because you can call foo(anything) in a generic function:</p> <pre><code>template &lt;typename T&gt; void bar(T x) { // stuff... foo(x); // more stuff... } </code></pre> <p>and get the most appropriate implementation at compile time. This is one way for C++ to achieve abstraction w/ minimal performance penalty.</p> <p>Hope it helps clearing up the concept of "partial specialization". In a way, this is how C++ do type pattern matching without needing the explicit pattern matching syntax (say the match keyword in Ocaml/F#), which sometimes gets in the way for generic programming. </p>
 

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