iterator begin() SPROUT_NOEXCEPT;
SPROUT_CONSTEXPR const_iterator begin() const SPROUT_NOEXCEPT;
#include <sprout/string.hpp>
using namespace sprout;
SPROUT_STATIC_CONSTEXPR auto input = string<8>("homuhomu");
static_assert(*input.begin() == 'h', "input first element is h.");