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    <p>Try this instead:</p> <pre><code>#include &lt;string&gt; #include &lt;vector&gt; #include &lt;iostream&gt; template&lt;typename U&gt; struct CheckSignature { enum {SizeTrue = 1, SizeFalse = 2}; typedef char ReturnTrue[SizeTrue]; typedef char ReturnFalse[SizeFalse]; typedef typename U::iterator (U::*InsertSig)(typename U::iterator, typename U::value_type const &amp;); template &lt;InsertSig f&gt; struct dummy_type { }; template &lt;typename T&gt; static ReturnTrue &amp;CheckInsert(T*, dummy_type&lt;&amp;T::insert&gt; dummy = dummy_type&lt;&amp;T::insert&gt;()); static ReturnFalse &amp;CheckInsert(...); static const bool value = (sizeof(CheckInsert(((U*)0))) == sizeof(ReturnTrue)); }; int main() { if(CheckSignature&lt;std::string &gt;::value) { std::cout &lt;&lt; "String class has proper insert function" &lt;&lt; std::endl; }; //OK, does not print, as expected. if(CheckSignature&lt;std::vector&lt;int&gt; &gt;::value) { std::cout &lt;&lt; "Vector class has proper insert function" &lt;&lt; std::endl; }; //OK, does print, as expected. return 0; } </code></pre> <p>The reason why it doesn't work is because, in your version, taking the address of the insert function will fail at the call site, not at the substitution (which is not an error). The above will make sure that if the type U (templated to T) cannot be used to obtain a member function pointer to insert which is convertable to the given signature, it will fail to substitute for the dummy parameter, and thus, revert to the ellipsis version.</p>
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    1. USMikael Persson
    1. USMikael Persson
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    1. COthat compiled for me, but `::value` was always false.
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    2. COah, in VisualStudio, vector::insert signature takes a `const_iterator` -- not an `iterator`. Once I changed the `InsertSig` typedef, it worked for me.
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    3. COAh, I didn't realize the ambiguity was with the various overloads of the insert() function, not CheckInsert(). Thanks!
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