library Decimal {
    using SafeMath for uint256;

    // ============ Constants ============

    uint256 constant BASE = 10**18;

    // ============ Structs ============

    struct D256 {
        uint256 value;
    }

    // ============ Static Functions ============

    function zero() internal pure returns (D256 memory) {
        return D256({value: 0});
    }

    function one() internal pure returns (D256 memory) {
        return D256({value: BASE});
    }

    function from(uint256 a) internal pure returns (D256 memory) {
        return D256({value: a.mul(BASE)});
    }

    function ratio(uint256 a, uint256 b) internal pure returns (D256 memory) {
        return D256({value: getPartial(a, BASE, b)});
    }

    // ============ Self Functions ============

    function add(D256 memory self, uint256 b)
        internal
        pure
        returns (D256 memory)
    {
        return D256({value: self.value.add(b.mul(BASE))});
    }

    function sub(D256 memory self, uint256 b)
        internal
        pure
        returns (D256 memory)
    {
        return D256({value: self.value.sub(b.mul(BASE))});
    }

    function sub(
        D256 memory self,
        uint256 b,
        string memory reason
    ) internal pure returns (D256 memory) {
        return D256({value: self.value.sub(b.mul(BASE), reason)});
    }

    function mul(D256 memory self, uint256 b)
        internal
        pure
        returns (D256 memory)
    {
        return D256({value: self.value.mul(b)});
    }

    function div(D256 memory self, uint256 b)
        internal
        pure
        returns (D256 memory)
    {
        return D256({value: self.value.div(b)});
    }

    function pow(D256 memory self, uint256 b)
        internal
        pure
        returns (D256 memory)
    {
        if (b == 0) {
            return from(1);
        }

        D256 memory temp = D256({value: self.value});
        for (uint256 i = 1; i < b; i++) {
            temp = mul(temp, self);
        }

        return temp;
    }

    function add(D256 memory self, D256 memory b)
        internal
        pure
        returns (D256 memory)
    {
        return D256({value: self.value.add(b.value)});
    }

    function sub(D256 memory self, D256 memory b)
        internal
        pure
        returns (D256 memory)
    {
        return D256({value: self.value.sub(b.value)});
    }

    function sub(
        D256 memory self,
        D256 memory b,
        string memory reason
    ) internal pure returns (D256 memory) {
        return D256({value: self.value.sub(b.value, reason)});
    }

    function mul(D256 memory self, D256 memory b)
        internal
        pure
        returns (D256 memory)
    {
        return D256({value: getPartial(self.value, b.value, BASE)});
    }

    function div(D256 memory self, D256 memory b)
        internal
        pure
        returns (D256 memory)
    {
        return D256({value: getPartial(self.value, BASE, b.value)});
    }

    function equals(D256 memory self, D256 memory b)
        internal
        pure
        returns (bool)
    {
        return self.value == b.value;
    }

    function greaterThan(D256 memory self, D256 memory b)
        internal
        pure
        returns (bool)
    {
        return compareTo(self, b) == 2;
    }

    function lessThan(D256 memory self, D256 memory b)
        internal
        pure
        returns (bool)
    {
        return compareTo(self, b) == 0;
    }

    function greaterThanOrEqualTo(D256 memory self, D256 memory b)
        internal
        pure
        returns (bool)
    {
        return compareTo(self, b) > 0;
    }

    function lessThanOrEqualTo(D256 memory self, D256 memory b)
        internal
        pure
        returns (bool)
    {
        return compareTo(self, b) < 2;
    }

    function isZero(D256 memory self) internal pure returns (bool) {
        return self.value == 0;
    }

    function asUint256(D256 memory self) internal pure returns (uint256) {
        return self.value.div(BASE);
    }

    // ============ Core Methods ============

    function getPartial(
        uint256 target,
        uint256 numerator,
        uint256 denominator
    ) private pure returns (uint256) {
        return target.mul(numerator).div(denominator);
    }

    function compareTo(D256 memory a, D256 memory b)
        private
        pure
        returns (uint256)
    {
        if (a.value == b.value) {
            return 1;
        }
        return a.value > b.value ? 2 : 0;
    }
}
function getPartial(
    uint256 target,
    uint256 numerator,
    uint256 denominator
) private pure returns (uint256) {
    return target.mul(numerator).div(denominator);
}

// ============ Core Methods ============