An unsigned 256 bit integer type for C++
This is simple implementation of an unsigned 256 bit integer type in C++. It's meant to be used like a standard uintX_t, except with a larger bit size than those provided by C/C++.
uint256_t requires uint128_t, which is included.
Be careful when initializing a uint128_t value. -1 does not create the value 2256 - 1. Rather, it uses 264 - 1, or whatever the built-in max unsigned value is, NOT 2128 - 1.