static char_type* assign(char_type* s, std::size_t n, char_type a);
#include <sprout/string.hpp>
#include <sprout/assert.hpp>
using namespace sprout;
char x[] = "homuhomu";
char_traits<char>::assign(x, 8, 'M');
SPROUT_ASSERT_MSG(x[0] == 'M', "x is filled by M.");