bitSlice.sol

/// @dev given a number get a slice of any bits, at certain offset
/// @param _n a number to be sliced
/// @param _nbits how many bits long is the new number
/// @param _offset how many bits to skip
function _sliceNumber(uint256 _n, uint256 _nbits, uint256 _offset) private pure returns (uint256) {
    // mask is made by shifting left an offset number of times
    uint256 mask = uint256((2**_nbits) - 1) << _offset;
    // AND n with mask, and trim to max of _nbits bits
    return uint256((_n & mask) >> _offset);
}

ref: https://medium.com/@imolfar/bitwise-operations-and-bit-manipulation-in-solidity-ethereum-1751f3d2e216

Nice concept. Very useful for generating verified randomness on-chain in blockchain.