static SPROUT_CXX14_CONSTEXPR char_type* copy(char_type* s1, char_type const* s2, std::size_t n);
#include <sprout/string.hpp>
#include <sprout/assert.hpp>
using namespace sprout;
char x[] = "homuhomu";
SPROUT_STATIC_CONSTEXPR char const* y = "madocchi";
int main() {
char_traits<char>::copy(x, y, 8);
SPROUT_ASSERT_MSG(x[0] == y[0], "y is copied to x.");
}