constexpr_if.cpp

#include<boost/hana.hpp>

namespace hana = boost::hana;

struct a_tag { };
struct b_tag { };

template <typename T>
constexpr auto get(T)
{
  if constexpr(T::value < 5)
    return hana::type_c<a_tag>;
  else
    return hana::type_c<b_tag>;
}

int main()
{
  static_assert(get(hana::int_c<0>) == hana::type_c<a_tag>);
  static_assert(get(hana::int_c<5>) == hana::type_c<b_tag>);
}