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POIs this partial function template specialization?
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copied!<p>I came up with this after answering <a href="https://stackoverflow.com/questions/10369464/template-function-gives-no-matching-function-for-call-error">this question</a></p> <p>I had a simple function template (C++11):</p> <pre><code>template<class elem_t, class list_t> bool in_list(const elem_t& elem, const list_t& list) { for (const auto& i : list) { if (elem == i) { return true; } } return false; } </code></pre> <p>But GCC emitted warnings because it doesn't seem to like deducing a template parameter as a std::initializer_list. So, without thinking, I made a specialization:</p> <pre><code>template<class elem_t> bool in_list(const elem_t& elem, std::initializer_list<elem_t> list) { for (const auto& i : list) { if (elem == i) { return true; } } return false; } </code></pre> <p>This worked. No more warnings. But when I looked again and thought about it, I remembered that C++ does not support partial template specialization on function templates. But that is what this appears to be. My only guess is that this is allowed because std::initializer_list is still dependent upon the template parameter, so it is, in essence, a different template. But I'm not sure if this is how it is supposed to be (isn't there a gotw about templates not overloading?).</p> <p>Is it standard behavior to accept this? And why?</p> <p>And as a bonus question, why does GCC not like deducing a template parameter as a std::initializer_list? It seems quite silly to expect me to copy and paste the code and just replace the parameter with a std::initializer_list.</p> <p>The warning message:</p> <pre><code>test.cpp: In function ‘int main()’: test.cpp:33:43: warning: deducing ‘const list_t’ as ‘const std::initializer_list<int>’ [enabled by default] test.cpp:6:6: warning: in call to ‘bool in_list(const elem_t&, const list_t&) [with elem_t = int, list_t = std::initializer_list<int>]’ [enabled by default] test.cpp:33:43: warning: (you can disable this with -fno-deduce-init-list) [enabled by default] </code></pre> <p>When called by <code>in_list(3, {1, 2, 3, 4, 5});</code></p> <p>EDIT: Apparently deducing a template parameter as an initializer_list is an extension according to the working draft for my version of GCC (<a href="http://gcc.gnu.org/onlinedocs/gcc-4.4.4/gcc/C_002b_002b-Dialect-Options.html" rel="nofollow noreferrer">cite</a>). So new question: Is this still an extension as of the final c++11 standard? If so, this would mean that it would be necessary for me to add the second function for standards-compliant code. Thanks for all your help! </p> <p>EDIT2: The compiler dialect flag appears to be removed for GCC 4.7, so it seems like the issue was resolved, but I don't know <em>how</em> it was resolved.</p>

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