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POWhat is the best way of renaming (alias/forward) a function in C++?
 

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  1. POWhat is the best way of renaming (alias/forward) a function in C++?
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    <p>(I'll restrict this question to C++11, since I believe there is no general way to do this in C++98).</p> <p>Supposed I have a complicated (in terms of signature) set of <em>template</em> functions and/or overloaded functions, and I want to use these functions in the exact same way but using a different name (that is, an alias).</p> <p>For example:</p> <pre><code>template&lt;class A, class B, class C&gt; D fun(A a, B&amp; b, C&amp;&amp; c){ ... } template&lt;class E, class F&gt; G fun(H&lt;E&gt; he, F&amp; f){ ... } ... many other versions of fun </code></pre> <p>Now suppose that I want to <em>rename</em> (or <em>alias</em>, or <em>forward</em> to be more precise) these functions, all at once (i.e. be able to use a different name for the same function without rewriting it). Such that, in other parts of the code I can use it with a different name and without modifying the above code.</p> <p>Is this the correct way to <em>rename</em> (alias/forward) <code>fun</code> into <code>gun</code>?</p> <pre><code>template&lt;typename... Args&gt; inline auto gun(Args&amp;&amp;... args)-&gt;decltype(fun(std::forward&lt;Args&gt;(args)...)){ return fun(std::forward&lt;Args&gt;(args)...); } </code></pre> <ul> <li>Is it truly general?</li> <li>Is this the simplest way?</li> <li>Is this the optimal way? (e.g. can be inlined, no unnecessary copies)</li> <li>What if the original function had some SFINAE features? (e.g. <code>template&lt;class A, class B, class C, class = std::enable_if&lt; ... &gt;::type&gt;</code>), will <code>decltype</code> transfer the SFINAE in all cases?</li> <li>What if the original function returned references? Isn't the decltype going to remove the references type?. (e.g. <code>double&amp; fun(double&amp; x){return x;}</code>).</li> <li>Can same be said about member functions?</li> </ul> <p>Clarification: <code>gun</code> is never going to be <em>exactly</em> <code>fun</code>, as the instances will have different addresses, but what I am looking for is a rename for the point of view of generic coding. </p> <p>Comment: I find strange that almost everything can be renamed/forwarded, namespaces, types (<code>typedef</code>) and template types <code>using typedef</code>, but not functions (or for that matter member functions).</p> <hr> <p><strong>EDIT</strong>: For completeness, and since this seems to be the way to do it, here I added a macro to define function aliases:</p> <pre><code>#define ALIAS_FUNCTION(OriginalnamE, AliasnamE) \ template &lt;typename... Args&gt; \ inline auto AliasnamE(Args&amp;&amp;... args) -&gt; decltype(OriginalnamE(std::forward&lt;Args&gt;(args)...)) { \ return OriginalnamE(std::forward&lt;Args&gt;(args)...); \ } </code></pre> <p>and then you use it like this:</p> <pre><code>namespace NS1{namepsace NS2{ ALIAS_FUNCTION(NSA::fun, gun); // second argument (target name can't have namespace) }} </code></pre>
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    1. COI think this is fine. `decltype` gets the correct type (i.e. `&` for a function that returns an lvalue reference, `&&` for a function that returns an rvalue reference, and non-reference otherwise).
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    2. COPlease, you'll make life a lot easier for everyone if you describe what you're actually doing. You're not renaming *anything*. The original name still exists. You're forwarding, or providing an alias or a wrapper function. None of this has anything to do with renaming. Renaming implies *changing* the name, making the old name go away in favor of a new one
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      1. POWhat is the best way of renaming (alias/forward) a function in C++?
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    3. CO@jalf, good point. I guess, it is harder to make the original name to go away. As the only way I imagine is to enclose the original definition into an unnamed namespace. But yes, that was not the idea.
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