template<typename Method, typename>
struct boost::hana::is_default< Method, typename >
Returns whether a tag-dispatched method implementation is a default implementation. 
Given a tag-dispatched method implementation method_impl<T...>, is_default<method_impl<T...>> returns whether method_impl<T...> is a default implementation. Note that if there is no default implementation for the method, then is_default should not be used unless a static assertion saying that "the method is not
implemented" is acceptable.
Example
 
 
#include <algorithm>
#include <iterator>
#include <sstream>
#include <vector>
 
 
template <typename T>
struct print_impl : hana::default_ {
    template <typename Stream, typename X>
    static void apply(Stream& out, X 
const& x)
 
    { out << x; }
};
 
auto print = [](
auto& stream, 
auto const& x) {
 
};
 
template <typename T>
struct print_impl<std::vector<T>> {
    template <typename Stream>
    static void apply(Stream& out, std::vector<T> 
const& xs) {
 
        out << '[';
        std::copy(begin(xs), end(xs), std::ostream_iterator<T>{out, ", "});
        out << ']';
    }
};
 
static_assert(hana::is_default<print_impl<int>>{}, "");
static_assert(!hana::is_default<print_impl<std::vector<int>>>{}, "");
 
int main() {
    {
        std::stringstream s;
        print(s, std::vector<int>{1, 2, 3});
 
    }
 
    {
        std::stringstream s;
    }
}
Defines macros to perform different kinds of assertions.
Defines boost::hana::default_ and boost::hana::is_default.
Defines boost::hana::tag_of and boost::hana::tag_of_t.
#define BOOST_HANA_RUNTIME_CHECK(...)
Equivalent to BOOST_HANA_RUNTIME_ASSERT, but not influenced by the BOOST_HANA_CONFIG_DISABLE_ASSERTIO...
Definition: assert.hpp:209
typename hana::tag_of< T >::type tag_of_t
Alias to tag_of<T>::type, provided for convenience.
Definition: tag_of.hpp:117
auto print
Returns a string representation of the given object.
Definition: printable.hpp:69
constexpr auto apply
Invokes a Callable with the given arguments.
Definition: apply.hpp:40
Namespace containing everything in the library.
Definition: accessors.hpp:20
  Inherits std::false_type.