template <size_t B, class D, bool S>
constexpr basic_integer<B * 2, D, S> fullmul(
const basic_integer<B, D, S>& lhs,
const basic_integer<B, D, S>& rhs
) noexcept;constexpr since C++14
Calculates result of product two integers and not truncates it.
Example
#include "fwnbi.hpp"
#include <iostream>
#include <iomanip>
int main() {
const auto max = fwnbi::uint128_t::max();
std::cout << std::hex;
std::cout << std::setw(64) << max << '\n';
std::cout << std::setw(64) << max * max << '\n';
std::cout << std::setw(64) << fwnbi::fullmul(max, max) << '\n';
}
Output
ffffffffffffffffffffffffffffffff
1
fffffffffffffffffffffffffffffffe00000000000000000000000000000001