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    <p>I find this to be the most elegant solution (and it is optimally forwarded):</p> <pre><code>#include &lt;cstddef&gt; #include &lt;tuple&gt; #include &lt;type_traits&gt; #include &lt;utility&gt; template&lt;size_t N&gt; struct Apply { template&lt;typename F, typename T, typename... A&gt; static inline auto apply(F &amp;&amp; f, T &amp;&amp; t, A &amp;&amp;... a) -&gt; decltype(Apply&lt;N-1&gt;::apply( ::std::forward&lt;F&gt;(f), ::std::forward&lt;T&gt;(t), ::std::get&lt;N-1&gt;(::std::forward&lt;T&gt;(t)), ::std::forward&lt;A&gt;(a)... )) { return Apply&lt;N-1&gt;::apply(::std::forward&lt;F&gt;(f), ::std::forward&lt;T&gt;(t), ::std::get&lt;N-1&gt;(::std::forward&lt;T&gt;(t)), ::std::forward&lt;A&gt;(a)... ); } }; template&lt;&gt; struct Apply&lt;0&gt; { template&lt;typename F, typename T, typename... A&gt; static inline auto apply(F &amp;&amp; f, T &amp;&amp;, A &amp;&amp;... a) -&gt; decltype(::std::forward&lt;F&gt;(f)(::std::forward&lt;A&gt;(a)...)) { return ::std::forward&lt;F&gt;(f)(::std::forward&lt;A&gt;(a)...); } }; template&lt;typename F, typename T&gt; inline auto apply(F &amp;&amp; f, T &amp;&amp; t) -&gt; decltype(Apply&lt; ::std::tuple_size&lt; typename ::std::decay&lt;T&gt;::type &gt;::value&gt;::apply(::std::forward&lt;F&gt;(f), ::std::forward&lt;T&gt;(t))) { return Apply&lt; ::std::tuple_size&lt; typename ::std::decay&lt;T&gt;::type &gt;::value&gt;::apply(::std::forward&lt;F&gt;(f), ::std::forward&lt;T&gt;(t)); } </code></pre> <p>Example usage:</p> <pre><code>void foo(int i, bool b); std::tuple&lt;int, bool&gt; t = make_tuple(20, false); void m() { apply(&amp;foo, t); } </code></pre> <p><s>Unfortunately GCC (4.6 at least) fails to compile this with "sorry, unimplemented: mangling overload" (which simply means that the compiler doesn't yet fully implement the C++11 spec), and since it uses variadic templates, it wont work in MSVC, so it is more or less useless. However, once there is a compiler that supports the spec, it will be the best approach IMHO. (Note: it isn't that hard to modify this so that you can work around the deficiencies in GCC, or to implement it with Boost Preprocessor, but it ruins the elegance, so this is the version I am posting.)</s></p> <p>GCC 4.7 now supports this code just fine.</p> <p>Edit: Added forward around actual function call to support rvalue reference form *this in case you are using clang (or if anybody else actually gets around to adding it).</p> <p>Edit: Added missing forward around the function object in the non-member apply function's body. Thanks to pheedbaq for pointing out that it was missing.</p> <p>Edit: And here is the C++14 version just since it is so much nicer (doesn't actually compile yet):</p> <pre><code>#include &lt;cstddef&gt; #include &lt;tuple&gt; #include &lt;type_traits&gt; #include &lt;utility&gt; template&lt;size_t N&gt; struct Apply { template&lt;typename F, typename T, typename... A&gt; static inline auto apply(F &amp;&amp; f, T &amp;&amp; t, A &amp;&amp;... a) { return Apply&lt;N-1&gt;::apply(::std::forward&lt;F&gt;(f), ::std::forward&lt;T&gt;(t), ::std::get&lt;N-1&gt;(::std::forward&lt;T&gt;(t)), ::std::forward&lt;A&gt;(a)... ); } }; template&lt;&gt; struct Apply&lt;0&gt; { template&lt;typename F, typename T, typename... A&gt; static inline auto apply(F &amp;&amp; f, T &amp;&amp;, A &amp;&amp;... a) { return ::std::forward&lt;F&gt;(f)(::std::forward&lt;A&gt;(a)...); } }; template&lt;typename F, typename T&gt; inline auto apply(F &amp;&amp; f, T &amp;&amp; t) { return Apply&lt; ::std::tuple_size&lt; ::std::decay_t&lt;T&gt; &gt;::value&gt;::apply(::std::forward&lt;F&gt;(f), ::std::forward&lt;T&gt;(t)); } </code></pre> <p>Here is a version for member functions (not tested very much!):</p> <pre><code>using std::forward; // You can change this if you like unreadable code or care hugely about namespace pollution. template&lt;size_t N&gt; struct ApplyMember { template&lt;typename C, typename F, typename T, typename... A&gt; static inline auto apply(C&amp;&amp; c, F&amp;&amp; f, T&amp;&amp; t, A&amp;&amp;... a) -&gt; decltype(ApplyMember&lt;N-1&gt;::apply(forward&lt;C&gt;(c), forward&lt;F&gt;(f), forward&lt;T&gt;(t), std::get&lt;N-1&gt;(forward&lt;T&gt;(t)), forward&lt;A&gt;(a)...)) { return ApplyMember&lt;N-1&gt;::apply(forward&lt;C&gt;(c), forward&lt;F&gt;(f), forward&lt;T&gt;(t), std::get&lt;N-1&gt;(forward&lt;T&gt;(t)), forward&lt;A&gt;(a)...); } }; template&lt;&gt; struct ApplyMember&lt;0&gt; { template&lt;typename C, typename F, typename T, typename... A&gt; static inline auto apply(C&amp;&amp; c, F&amp;&amp; f, T&amp;&amp;, A&amp;&amp;... a) -&gt; decltype((forward&lt;C&gt;(c)-&gt;*forward&lt;F&gt;(f))(forward&lt;A&gt;(a)...)) { return (forward&lt;C&gt;(c)-&gt;*forward&lt;F&gt;(f))(forward&lt;A&gt;(a)...); } }; // C is the class, F is the member function, T is the tuple. template&lt;typename C, typename F, typename T&gt; inline auto apply(C&amp;&amp; c, F&amp;&amp; f, T&amp;&amp; t) -&gt; decltype(ApplyMember&lt;std::tuple_size&lt;typename std::decay&lt;T&gt;::type&gt;::value&gt;::apply(forward&lt;C&gt;(c), forward&lt;F&gt;(f), forward&lt;T&gt;(t))) { return ApplyMember&lt;std::tuple_size&lt;typename std::decay&lt;T&gt;::type&gt;::value&gt;::apply(forward&lt;C&gt;(c), forward&lt;F&gt;(f), forward&lt;T&gt;(t)); } </code></pre> <pre><code>// Example: class MyClass { public: void foo(int i, bool b); }; MyClass mc; std::tuple&lt;int, bool&gt; t = make_tuple(20, false); void m() { apply(&amp;mc, &amp;MyClass::foo, t); } </code></pre>
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    1. POHow do I expand a tuple into variadic template function's arguments?
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    1. CO+1 out of the answers listed, yours was the closest I could get to working with arguments whose arguments are vectors... ...but I am still getting compile errors. http://ideone.com/xH5kBH If you compile this with -DDIRECT_CALL and run it, you will see what the output should be. I get a compile error otherwise (I think decltype is not smart enough to figure out my special case), with gcc 4.7.2.
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    2. COThe version of gcc on ideaone is to old for this to pass, it doesn't support the mangled decltype return type overloading. I have tested this code relatively thoroughly in gcc 4.7.2, and I haven't run into any problems. With gcc 4.8, you can use the new C++17 automatic return value feature to avoid all the nasty decltype trailing return types.
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    3. CO+1 I really like that automatic return value feature - thx for the heads up
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