contract DSMath {
    
    /*
    standard uint256 functions
     */

    function add(uint256 x, uint256 y) pure internal returns (uint256 z) {
        assert((z = x + y) >= x);
    }

    function sub(uint256 x, uint256 y) pure internal returns (uint256 z) {
        assert((z = x - y) <= x);
    }

    function mul(uint256 x, uint256 y) pure internal returns (uint256 z) {
        assert(y == 0 || (z = x * y) / y == x);
    }

    function div(uint256 x, uint256 y) pure internal returns (uint256 z) {
        z = x / y;
    }

    function min(uint256 x, uint256 y) pure internal returns (uint256 z) {
        return x <= y ? x : y;
    }
    function max(uint256 x, uint256 y) pure internal returns (uint256 z) {
        return x >= y ? x : y;
    }

    /*
    uint128 functions (h is for half)
     */


    function hadd(uint128 x, uint128 y) pure internal returns (uint128 z) {
        assert((z = x + y) >= x);
    }

    function hsub(uint128 x, uint128 y) pure internal returns (uint128 z) {
        assert((z = x - y) <= x);
    }

    function hmul(uint128 x, uint128 y) pure internal returns (uint128 z) {
        assert(y == 0 || (z = x * y) / y == x);
    }

    function hdiv(uint128 x, uint128 y) pure internal returns (uint128 z) {
        z = x / y;
    }

    function hmin(uint128 x, uint128 y) pure internal returns (uint128 z) {
        return x <= y ? x : y;
    }
    function hmax(uint128 x, uint128 y) pure internal returns (uint128 z) {
        return x >= y ? x : y;
    }


    /*
    int256 functions
     */

    function imin(int256 x, int256 y) pure internal returns (int256 z) {
        return x <= y ? x : y;
    }
    function imax(int256 x, int256 y) pure internal returns (int256 z) {
        return x >= y ? x : y;
    }

    /*
    WAD math
     */

    uint128 constant WAD = 10 ** 18;

    function wadd(uint128 x, uint128 y) pure internal returns (uint128) {
        return hadd(x, y);
    }

    function wsub(uint128 x, uint128 y) pure internal returns (uint128) {
        return hsub(x, y);
    }

    function wmul(uint128 x, uint128 y) pure internal returns (uint128 z) {
        z = cast(add(mul(uint256(x), y), WAD/2) / WAD);
    }

    function wdiv(uint128 x, uint128 y) pure internal returns (uint128 z) {
        z = cast(add(mul(uint256(x), WAD), y/2) / y);
    }

    function wmin(uint128 x, uint128 y) pure internal returns (uint128) {
        return hmin(x, y);
    }
    function wmax(uint128 x, uint128 y) pure internal returns (uint128) {
        return hmax(x, y);
    }

    /*
    RAY math
     */

    uint128 constant RAY = 10 ** 27;

    function radd(uint128 x, uint128 y) pure internal returns (uint128) {
        return hadd(x, y);
    }

    function rsub(uint128 x, uint128 y) pure internal returns (uint128) {
        return hsub(x, y);
    }

    function rmul(uint128 x, uint128 y) pure internal returns (uint128 z) {
        z = cast(add(mul(uint256(x), y), RAY/2) / RAY);
    }

    function rdiv(uint128 x, uint128 y) pure internal returns (uint128 z) {
        z = cast(add(mul(uint256(x), RAY), y/2) / y);
    }

    function rpow(uint128 x, uint64 n) pure internal returns (uint128 z) {
        // This famous algorithm is called "exponentiation by squaring"
        // and calculates x^n with x as fixed-point and n as regular unsigned.
        //
        // It's O(log n), instead of O(n) for naive repeated multiplication.
        //
        // These facts are why it works:
        //
        //  If n is even, then x^n = (x^2)^(n/2).
        //  If n is odd,  then x^n = x * x^(n-1),
        //   and applying the equation for even x gives
        //    x^n = x * (x^2)^((n-1) / 2).
        //
        //  Also, EVM division is flooring and
        //    floor[(n-1) / 2] = floor[n / 2].

        z = n % 2 != 0 ? x : RAY;

        for (n /= 2; n != 0; n /= 2) {
            x = rmul(x, x);

            if (n % 2 != 0) {
                z = rmul(z, x);
            }
        }
    }

    function rmin(uint128 x, uint128 y) pure internal returns (uint128) {
        return hmin(x, y);
    }
    function rmax(uint128 x, uint128 y) pure internal returns (uint128) {
        return hmax(x, y);
    }

    function cast(uint256 x) pure internal returns (uint128 z) {
        assert((z = uint128(x)) == x);
    }

}
function add(uint256 x, uint256 y) pure internal returns (uint256 z) {
    assert((z = x + y) >= x);
}

/*
 standard uint256 functions
 */