How can I detect if a type can be streamed to an std::ostream?

Question

I\'m trying to write a type trait to detect if a type has overloaded operator<<() suitable to use to an output stream.

I\'m missing something because I\'m alwa

Answer 1

And to test for '>>' operator:

template class is_istreamable
{
    template
    static auto test (int) -> decltype (std::declval() >> std::declval(), std::true_type ());

    template
    static auto test (...) -> std::false_type;

public:

    static const bool value = decltype (test (0))::value;
};