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copied!<p>I think you need to use template template syntax to pass a parameter whose type is a template dependent on another template like this:</p> <pre><code>template <template<class> class H, class S> void f(const H<S> &value) { } </code></pre> <p>Here, <code>H</code> is a template, but I wanted this function to deal with all specializations of <code>H</code>.</p> <p><strong>NOTE</strong>: I've been programming c++ for many years and have only needed this once. I find that it is a rarely needed feature (of course handy when you need it!).</p> <p>I've been trying to think of good examples, and to be honest, most of the time this isn't necessary, but let's contrive an example. Let's pretend that <code>std::vector</code> <em>doesn't</em> have a <code>typedef value_type</code>. </p> <p>So how would you write a function which can create variables of the right type for the vectors elements? This would work.</p> <pre><code>template <template<class, class> class V, class T, class A> void f(V<T, A> &v) { // This can be "typename V<T, A>::value_type", // but we are pretending we don't have it T temp = v.back(); v.pop_back(); // Do some work on temp std::cout << temp << std::endl; } </code></pre> <p><strong>NOTE</strong>: we <code>std::vector</code> has two template parameters, type and allocator, so we had to accept both of them. Fortunately, because of type deduction, we won't need to write out the exact type explicitly.</p> <p>which you can use like this:</p> <pre><code>f<std::vector, int>(v); // v is of type std::vector<int> using any allocator </code></pre> <p>or better yet, we can just use:</p> <pre><code>f(v); // everything is deduced, f can deal with a vector of any type! </code></pre> <p><strong>UPDATE</strong>: Even this contrived example, while illustrative, is no longer an amazing example due to c++11 introducing <code>auto</code>. Now the same function can be written as:</p> <pre><code>template <class Cont> void f(Cont &v) { auto temp = v.back(); v.pop_back(); // Do some work on temp std::cout << temp << std::endl; } </code></pre> <p>which is how I'd prefer to write this type of code.</p>

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