Check if template type is any instantiation of std::array

Question

I'm in need of some compile time check if a template type passed into a templated function is any instantiation of std::array

Like

IsStdArray<std::array<float, 12>>::value; // should evaluate to true
IsStdArray<std::array<int, 1000>>::value; // should evaluate to true
IsStdArray<std::vector<float>>::value;    // should evaluate to false
IsStdArray<std::string>::value            // should evaluate to false

I'm especially struggling to come up with anything that is independent of the array size. Note, that a function returning a constexpr bool would be fine as solution too!

Answer 1

You can partially specialise a trait class.

template<typename T>
struct IsStdArray : std::false_type {};

template<typename T, std::size_t N>
struct IsStdArray<std::array<T, N>> : std::true_type {};