如何在C ++中专门化std :: vector的模板模板参数

Question

I need a specialization of this code:

template < class T, class Alloc, template <class, class> class VECTOR >
void function(const VECTOR<T, Alloc> &argument);

for a template std::vector. For now, it works with any 2-argument template ("class VECTOR") argument.

In other words:

// A, B -- any unpredictable types

function< std::vector <A, B> > (arg);            // specialization
function< Some2ArgsTemplate <A, B> > (arg);      // general
function< SomeOther2ArgsTemplate <A, B> > (arg); // general

Is it possible to implement that with no knowledge about A and B? Any C++11/C++14 ideas are OK.

Answer 1

Don't specialize, overload:

template < class T, class Alloc>
void function(const std::vector<T, Alloc> &argument);

This will be preferred in you pass in a std::vector as opposed to any other 2-type class template (eg std::list ). And it will be preferred in a consistent, easy-to-reason about way. Also, you can't partially specialize function templates anyway.

Explicit function template specialization is... problematic . The order that you write your specializations could be significant!

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Note that this syntax isn't correct:

function< Some2ArgsTemplate <A, B> > (arg);

Explicitly specified template arguments go left-to-right. So here you're specifying T to be Some2ArgsTemplate <A, B> ... which probably prevents deduction from succeeding. You shouldn't need to explicitly specify anything:

Some2ArgTemplate<A, B> arg = ...;
function(arg); // deduce T=A, Alloc=B, VECTOR=Some2ArgTemplate