Contract Source Code:

// SPDX-License-Identifier: SEE LICENSE IN LICENSE

pragma solidity 0.5.17;

interface IValueLiquidFactory {
    event PairCreated(address indexed token0, address indexed token1, address pair, uint32 tokenWeight0, uint32 swapFee, uint256);

    function feeTo() external view returns (address);

    function formula() external view returns (address);

    function protocolFee() external view returns (uint256);

    function feeToSetter() external view returns (address);

    function getPair(
        address tokenA,
        address tokenB,
        uint32 tokenWeightA,
        uint32 swapFee
    ) external view returns (address pair);

    function allPairs(uint256) external view returns (address pair);

    function isPair(address) external view returns (bool);

    function allPairsLength() external view returns (uint256);

    function createPair(
        address tokenA,
        address tokenB,
        uint32 tokenWeightA,
        uint32 swapFee
    ) external returns (address pair);

    function getWeightsAndSwapFee(address pair)
        external
        view
        returns (
            uint32 tokenWeight0,
            uint32 tokenWeight1,
            uint32 swapFee
        );

    function setFeeTo(address) external;

    function setFeeToSetter(address) external;

    function setProtocolFee(uint256) external;
}

interface IValueLiquidPair {
    event Approval(address indexed owner, address indexed spender, uint256 value);
    event Transfer(address indexed from, address indexed to, uint256 value);

    function name() external view returns (string memory);

    function symbol() external view returns (string memory);

    function decimals() external pure returns (uint8);

    function totalSupply() external view returns (uint256);

    function balanceOf(address owner) external view returns (uint256);

    function allowance(address owner, address spender) external view returns (uint256);

    function approve(address spender, uint256 value) external returns (bool);

    function transfer(address to, uint256 value) external returns (bool);

    function transferFrom(
        address from,
        address to,
        uint256 value
    ) external returns (bool);

    function DOMAIN_SEPARATOR() external view returns (bytes32);

    function PERMIT_TYPEHASH() external pure returns (bytes32);

    function nonces(address owner) external view returns (uint256);

    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external;

    event PaidProtocolFee(uint112 collectedFee0, uint112 collectedFee1);
    event Mint(address indexed sender, uint256 amount0, uint256 amount1);
    event Burn(address indexed sender, uint256 amount0, uint256 amount1, address indexed to);
    event Swap(address indexed sender, uint256 amount0In, uint256 amount1In, uint256 amount0Out, uint256 amount1Out, address indexed to);
    event Sync(uint112 reserve0, uint112 reserve1);

    function MINIMUM_LIQUIDITY() external pure returns (uint256);

    function factory() external view returns (address);

    function token0() external view returns (address);

    function token1() external view returns (address);

    function getReserves()
        external
        view
        returns (
            uint112 reserve0,
            uint112 reserve1,
            uint32 blockTimestampLast
        );

    function getCollectedFees() external view returns (uint112 _collectedFee0, uint112 _collectedFee1);

    function getTokenWeights() external view returns (uint32 tokenWeight0, uint32 tokenWeight1);

    function getSwapFee() external view returns (uint32);

    function price0CumulativeLast() external view returns (uint256);

    function price1CumulativeLast() external view returns (uint256);

    function mint(address to) external returns (uint256 liquidity);

    function burn(address to) external returns (uint256 amount0, uint256 amount1);

    function swap(
        uint256 amount0Out,
        uint256 amount1Out,
        address to,
        bytes calldata data
    ) external;

    function skim(address to) external;

    function sync() external;

    function initialize(
        address,
        address,
        uint32,
        uint32
    ) external;
}

// SPDX-License-Identifier: SEE LICENSE IN LICENSE
/*
    Bancor Formula interface
*/
interface IValueLiquidFormula {
    function getReserveAndWeights(address pair, address tokenA)
        external
        view
        returns (
            address tokenB,
            uint256 reserveA,
            uint256 reserveB,
            uint32 tokenWeightA,
            uint32 tokenWeightB,
            uint32 swapFee
        );

    function getFactoryReserveAndWeights(
        address factory,
        address pair,
        address tokenA
    )
        external
        view
        returns (
            address tokenB,
            uint256 reserveA,
            uint256 reserveB,
            uint32 tokenWeightA,
            uint32 tokenWeightB,
            uint32 swapFee
        );

    function getAmountIn(
        uint256 amountOut,
        uint256 reserveIn,
        uint256 reserveOut,
        uint32 tokenWeightIn,
        uint32 tokenWeightOut,
        uint32 swapFee
    ) external view returns (uint256 amountIn);

    function getPairAmountIn(
        address pair,
        address tokenIn,
        uint256 amountOut
    ) external view returns (uint256 amountIn);

    function getAmountOut(
        uint256 amountIn,
        uint256 reserveIn,
        uint256 reserveOut,
        uint32 tokenWeightIn,
        uint32 tokenWeightOut,
        uint32 swapFee
    ) external view returns (uint256 amountOut);

    function getPairAmountOut(
        address pair,
        address tokenIn,
        uint256 amountIn
    ) external view returns (uint256 amountOut);

    function getAmountsIn(
        address tokenIn,
        address tokenOut,
        uint256 amountOut,
        address[] calldata path
    ) external view returns (uint256[] memory amounts);

    function getFactoryAmountsIn(
        address factory,
        address tokenIn,
        address tokenOut,
        uint256 amountOut,
        address[] calldata path
    ) external view returns (uint256[] memory amounts);

    function getAmountsOut(
        address tokenIn,
        address tokenOut,
        uint256 amountIn,
        address[] calldata path
    ) external view returns (uint256[] memory amounts);

    function getFactoryAmountsOut(
        address factory,
        address tokenIn,
        address tokenOut,
        uint256 amountIn,
        address[] calldata path
    ) external view returns (uint256[] memory amounts);

    function ensureConstantValue(
        uint256 reserve0,
        uint256 reserve1,
        uint256 balance0Adjusted,
        uint256 balance1Adjusted,
        uint32 tokenWeight0
    ) external view returns (bool);

    function getReserves(
        address pair,
        address tokenA,
        address tokenB
    ) external view returns (uint256 reserveA, uint256 reserveB);

    function getOtherToken(address pair, address tokenA) external view returns (address tokenB);

    function quote(
        uint256 amountA,
        uint256 reserveA,
        uint256 reserveB
    ) external pure returns (uint256 amountB);

    function sortTokens(address tokenA, address tokenB) external pure returns (address token0, address token1);

    function mintLiquidityFee(
        uint256 totalLiquidity,
        uint112 reserve0,
        uint112 reserve1,
        uint32 tokenWeight0,
        uint32 tokenWeight1,
        uint112 collectedFee0,
        uint112 collectedFee1
    ) external view returns (uint256 amount);
}

interface IValueLiquidERC20 {
    event Approval(address indexed owner, address indexed spender, uint256 value);
    event Transfer(address indexed from, address indexed to, uint256 value);

    function name() external view returns (string memory);

    function symbol() external view returns (string memory);

    function decimals() external pure returns (uint8);

    function totalSupply() external view returns (uint256);

    function balanceOf(address owner) external view returns (uint256);

    function allowance(address owner, address spender) external view returns (uint256);

    function approve(address spender, uint256 value) external returns (bool);

    function transfer(address to, uint256 value) external returns (bool);

    function transferFrom(
        address from,
        address to,
        uint256 value
    ) external returns (bool);

    function DOMAIN_SEPARATOR() external view returns (bytes32);

    function PERMIT_TYPEHASH() external pure returns (bytes32);

    function nonces(address owner) external view returns (uint256);

    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external;
}

// a library for performing overflow-safe math, courtesy of DappHub (https://github.com/dapphub/ds-math)
library SafeMath {
    function add(uint256 x, uint256 y) internal pure returns (uint256 z) {
        require((z = x + y) >= x, "ds-math-add-overflow");
    }

    function sub(uint256 x, uint256 y) internal pure returns (uint256 z) {
        require((z = x - y) <= x, "ds-math-sub-underflow");
    }

    function mul(uint256 x, uint256 y) internal pure returns (uint256 z) {
        require(y == 0 || (z = x * y) / y == x, "ds-math-mul-overflow");
    }

    function div(uint256 a, uint256 b) internal pure returns (uint256 c) {
        require(b > 0, "ds-math-division-by-zero");
        c = a / b;
    }
}

contract ValueLiquidERC20 is IValueLiquidERC20 {
    using SafeMath for uint256;

    string public name;
    string public symbol;
    uint8 public constant decimals = 18;
    uint256 public totalSupply;
    mapping(address => uint256) public balanceOf;
    mapping(address => mapping(address => uint256)) public allowance;

    bytes32 public DOMAIN_SEPARATOR;
    // keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");
    bytes32 public constant PERMIT_TYPEHASH = 0x6e71edae12b1b97f4d1f60370fef10105fa2faae0126114a169c64845d6126c9;
    mapping(address => uint256) public nonces;

    constructor() public {}

    function initialize(string memory _name, string memory _symbol) internal {
        name = _name;
        symbol = _symbol;
        uint256 chainId;
        assembly {
            chainId := chainid()
        }
        DOMAIN_SEPARATOR = keccak256(
            abi.encode(
                keccak256("EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)"),
                keccak256(bytes(_name)),
                keccak256(bytes("1")),
                chainId,
                address(this)
            )
        );
    }

    function _mint(address to, uint256 value) internal {
        totalSupply = totalSupply.add(value);
        balanceOf[to] = balanceOf[to].add(value);
        emit Transfer(address(0), to, value);
    }

    function _burn(address from, uint256 value) internal {
        balanceOf[from] = balanceOf[from].sub(value);
        totalSupply = totalSupply.sub(value);
        emit Transfer(from, address(0), value);
    }

    function _approve(
        address owner,
        address spender,
        uint256 value
    ) private {
        allowance[owner][spender] = value;
        emit Approval(owner, spender, value);
    }

    function _transfer(
        address from,
        address to,
        uint256 value
    ) private {
        balanceOf[from] = balanceOf[from].sub(value);
        balanceOf[to] = balanceOf[to].add(value);
        emit Transfer(from, to, value);
    }

    function approve(address spender, uint256 value) external returns (bool) {
        _approve(msg.sender, spender, value);
        return true;
    }

    function transfer(address to, uint256 value) external returns (bool) {
        _transfer(msg.sender, to, value);
        return true;
    }

    function transferFrom(
        address from,
        address to,
        uint256 value
    ) external returns (bool) {
        if (allowance[from][msg.sender] != uint256(-1)) {
            allowance[from][msg.sender] = allowance[from][msg.sender].sub(value);
        }
        _transfer(from, to, value);
        return true;
    }

    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external {
        require(deadline >= block.timestamp, "VLP: EXPIRED");
        bytes32 digest =
            keccak256(abi.encodePacked("\x19\x01", DOMAIN_SEPARATOR, keccak256(abi.encode(PERMIT_TYPEHASH, owner, spender, value, nonces[owner]++, deadline))));
        address recoveredAddress = ecrecover(digest, v, r, s);
        require(recoveredAddress != address(0) && recoveredAddress == owner, "VLP: INVALID_SIGNATURE");
        _approve(owner, spender, value);
    }
}

// a library for performing various math operations
library Math {
    function min(uint256 x, uint256 y) internal pure returns (uint256 z) {
        z = x < y ? x : y;
    }

    // babylonian method (https://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Babylonian_method)
    function sqrt(uint256 y) internal pure returns (uint256 z) {
        if (y > 3) {
            z = y;
            uint256 x = y / 2 + 1;
            while (x < z) {
                z = x;
                x = (y / x + x) / 2;
            }
        } else if (y != 0) {
            z = 1;
        }
    }
}

// a library for handling binary fixed point numbers (https://en.wikipedia.org/wiki/Q_(number_format))
// range: [0, 2**112 - 1]
// resolution: 1 / 2**112
library UQ112x112 {
    uint224 constant Q112 = 2**112;

    // encode a uint112 as a UQ112x112
    function encode(uint112 y) internal pure returns (uint224 z) {
        z = uint224(y) * Q112; // never overflows
    }

    // divide a UQ112x112 by a uint112, returning a UQ112x112
    function uqdiv(uint224 x, uint112 y) internal pure returns (uint224 z) {
        z = x / uint224(y);
    }
}

interface IERC20 {
    event Approval(address indexed owner, address indexed spender, uint256 value);
    event Transfer(address indexed from, address indexed to, uint256 value);

    function name() external view returns (string memory);

    function symbol() external view returns (string memory);

    function decimals() external view returns (uint8);

    function totalSupply() external view returns (uint256);

    function balanceOf(address owner) external view returns (uint256);

    function allowance(address owner, address spender) external view returns (uint256);

    function approve(address spender, uint256 value) external returns (bool);

    function transfer(address to, uint256 value) external returns (bool);

    function transferFrom(
        address from,
        address to,
        uint256 value
    ) external returns (bool);
}

interface IUniswapV2Callee {
    function uniswapV2Call(
        address sender,
        uint256 amount0,
        uint256 amount1,
        bytes calldata data
    ) external;
}

contract ValueLiquidPair is IValueLiquidPair, ValueLiquidERC20 {
    using SafeMath for uint256;
    using UQ112x112 for uint224;

    uint256 public constant MINIMUM_LIQUIDITY = 10**3;
    bytes4 private constant SELECTOR = bytes4(keccak256(bytes("transfer(address,uint256)")));

    address public factory;
    address public token0;
    address public token1;

    uint112 private reserve0; // uses single storage slot, accessible via getReserves
    uint112 private reserve1; // uses single storage slot, accessible via getReserves
    uint32 private blockTimestampLast; // uses single storage slot, accessible via getReserves
    uint256 public price0CumulativeLast;
    uint256 public price1CumulativeLast;
    uint256 private unlocked = 1;
    address public formula;

    uint112 private collectedFee0; // uses single storage slot, accessible via getReserves
    uint112 private collectedFee1; // uses single storage slot, accessible via getReserves
    uint32 private tokenWeight0;

    uint32 private swapFee;

    modifier lock() {
        require(unlocked == 1, "VLP: LOCKED");
        unlocked = 0;
        _;
        unlocked = 1;
    }

    function getReserves()
        public
        view
        returns (
            uint112 _reserve0,
            uint112 _reserve1,
            uint32 _blockTimestampLast
        )
    {
        _reserve0 = reserve0;
        _reserve1 = reserve1;
        _blockTimestampLast = blockTimestampLast;
    }

    function getCollectedFees() public view returns (uint112 _collectedFee0, uint112 _collectedFee1) {
        _collectedFee0 = collectedFee0;
        _collectedFee1 = collectedFee1;
    }

    function getTokenWeights() public view returns (uint32 _tokenWeight0, uint32 _tokenWeight1) {
        _tokenWeight0 = tokenWeight0;
        _tokenWeight1 = 100 - tokenWeight0;
    }

    function getSwapFee() public view returns (uint32 _swapFee) {
        _swapFee = swapFee;
    }

    function _safeTransfer(
        address token,
        address to,
        uint256 value
    ) private {
        (bool success, bytes memory data) = token.call(abi.encodeWithSelector(SELECTOR, to, value));
        require(success && (data.length == 0 || abi.decode(data, (bool))), "VLP: TRANSFER_FAILED");
    }

    constructor() public {
        factory = msg.sender;
    }

    // called once by the factory at time of deployment
    function initialize(
        address _token0,
        address _token1,
        uint32 _tokenWeight0,
        uint32 _swapFee
    ) external {
        require(msg.sender == factory, "VLP: FORBIDDEN");
        string memory _symbol0 = IERC20(_token0).symbol();
        string memory _symbol1 = IERC20(_token1).symbol();
        initialize(string(abi.encodePacked(_symbol0, "/", _symbol1, " Value LP")), string(abi.encodePacked(_symbol0, _symbol1)));
        // sufficient check
        token0 = _token0;
        token1 = _token1;
        tokenWeight0 = _tokenWeight0;
        swapFee = _swapFee;
        formula = IValueLiquidFactory(factory).formula();
    }

    // update reserves and, on the first call per block, price accumulators
    function _update(
        uint256 balance0,
        uint256 balance1,
        uint112 _reserve0,
        uint112 _reserve1
    ) private {
        uint32 _tokenWeight0 = tokenWeight0;
        require(balance0 * (100 - _tokenWeight0) <= uint112(-1) && balance1 * _tokenWeight0 <= uint112(-1), "VLP: OVERFLOW");
        uint32 blockTimestamp = uint32(block.timestamp % 2**32);
        uint32 timeElapsed = blockTimestamp - blockTimestampLast;
        // overflow is desired
        if (timeElapsed > 0 && _reserve0 != 0 && _reserve1 != 0) {
            // * never overflows, and + overflow is desired
            uint112 mReserve0 = _reserve0 * (100 - _tokenWeight0);
            uint112 mReserve1 = _reserve1 * _tokenWeight0;
            price0CumulativeLast += uint256(UQ112x112.encode(mReserve1).uqdiv(mReserve0)) * timeElapsed;
            price1CumulativeLast += uint256(UQ112x112.encode(mReserve0).uqdiv(mReserve1)) * timeElapsed;
        }
        reserve0 = uint112(balance0);
        reserve1 = uint112(balance1);
        blockTimestampLast = blockTimestamp;
        emit Sync(reserve0, reserve1);
    }

    function _mintFee(uint112 _reserve0, uint112 _reserve1) private returns (bool feeOn) {
        address feeTo = IValueLiquidFactory(factory).feeTo();
        uint112 protocolFee = uint112(IValueLiquidFactory(factory).protocolFee());
        feeOn = feeTo != address(0);
        (uint112 _collectedFee0, uint112 _collectedFee1) = getCollectedFees();
        if (protocolFee > 0 && feeOn && (_collectedFee0 > 0 || _collectedFee1 > 0)) {
            uint32 _tokenWeight0 = tokenWeight0;
            uint256 liquidity =
                IValueLiquidFormula(formula).mintLiquidityFee(
                    totalSupply,
                    _reserve0,
                    _reserve1,
                    _tokenWeight0,
                    100 - _tokenWeight0,
                    _collectedFee0 / protocolFee,
                    _collectedFee1 / protocolFee
                );
            if (liquidity > 0) _mint(feeTo, liquidity);
        }
        if (_collectedFee0 > 0) collectedFee0 = 0;
        if (_collectedFee1 > 0) collectedFee1 = 0;
    }

    // this low-level function should be called from a contract which performs important safety checks
    function mint(address to) external lock returns (uint256 liquidity) {
        (uint112 _reserve0, uint112 _reserve1, ) = getReserves(); // gas savings
        uint256 balance0 = IERC20(token0).balanceOf(address(this));
        uint256 balance1 = IERC20(token1).balanceOf(address(this));
        uint256 amount0 = balance0.sub(_reserve0);
        uint256 amount1 = balance1.sub(_reserve1);
        _mintFee(_reserve0, _reserve1);
        uint256 _totalSupply = totalSupply;
        // gas savings, must be defined here since totalSupply can update in _mintFee
        if (_totalSupply == 0) {
            liquidity = Math.sqrt(amount0.mul(amount1)).sub(MINIMUM_LIQUIDITY);
            _mint(address(0), MINIMUM_LIQUIDITY);
            // permanently lock the first MINIMUM_LIQUIDITY tokens
        } else {
            liquidity = Math.min(amount0.mul(_totalSupply) / _reserve0, amount1.mul(_totalSupply) / _reserve1);
        }
        require(liquidity > 0, "VLP: INSUFFICIENT_LIQUIDITY_MINTED");
        _mint(to, liquidity);

        _update(balance0, balance1, _reserve0, _reserve1);
        emit Mint(msg.sender, amount0, amount1);
    }

    // this low-level function should be called from a contract which performs important safety checks
    function burn(address to) external lock returns (uint256 amount0, uint256 amount1) {
        (uint112 _reserve0, uint112 _reserve1, ) = getReserves(); // gas savings
        address _token0 = token0; // gas savings
        address _token1 = token1; // gas savings
        uint256 balance0 = IERC20(_token0).balanceOf(address(this));
        uint256 balance1 = IERC20(_token1).balanceOf(address(this));
        uint256 liquidity = balanceOf[address(this)];
        _mintFee(_reserve0, _reserve1);
        uint256 _totalSupply = totalSupply; // gas savings, must be defined here since totalSupply can update in _mintFee
        amount0 = liquidity.mul(balance0) / _totalSupply; // using balances ensures pro-rata distribution
        amount1 = liquidity.mul(balance1) / _totalSupply; // using balances ensures pro-rata distribution
        require(amount0 > 0 && amount1 > 0, "VLP: INSUFFICIENT_LIQUIDITY_BURNED");
        _burn(address(this), liquidity);
        _safeTransfer(_token0, to, amount0);
        _safeTransfer(_token1, to, amount1);
        balance0 = IERC20(_token0).balanceOf(address(this));
        balance1 = IERC20(_token1).balanceOf(address(this));

        _update(balance0, balance1, _reserve0, _reserve1);
        emit Burn(msg.sender, amount0, amount1, to);
    }

    // this low-level function should be called from a contract which performs important safety checks
    function swap(
        uint256 amount0Out,
        uint256 amount1Out,
        address to,
        bytes calldata data
    ) external lock {
        require(amount0Out > 0 || amount1Out > 0, "VLP: INSUFFICIENT_OUTPUT_AMOUNT");
        uint112 _reserve0 = reserve0; // gas savings
        uint112 _reserve1 = reserve1; // gas savings
        require(amount0Out < _reserve0 && amount1Out < _reserve1, "VLP: INSUFFICIENT_LIQUIDITY");

        uint256 balance0;
        uint256 balance1;
        {
            // scope for _token{0,1}, avoids stack too deep errors
            address _token0 = token0;
            address _token1 = token1;
            require(to != _token0 && to != _token1, "VLP: INVALID_TO");
            if (amount0Out > 0) _safeTransfer(_token0, to, amount0Out); // optimistically transfer tokens
            if (amount1Out > 0) _safeTransfer(_token1, to, amount1Out); // optimistically transfer tokens
            if (data.length > 0) IUniswapV2Callee(to).uniswapV2Call(msg.sender, amount0Out, amount1Out, data);
            balance0 = IERC20(_token0).balanceOf(address(this));
            balance1 = IERC20(_token1).balanceOf(address(this));
        }
        uint256 amount0In = balance0 > _reserve0 - amount0Out ? balance0 - (_reserve0 - amount0Out) : 0;
        uint256 amount1In = balance1 > _reserve1 - amount1Out ? balance1 - (_reserve1 - amount1Out) : 0;
        require(amount0In > 0 || amount1In > 0, "VLP: INSUFFICIENT_INPUT_AMOUNT");
        {
            // scope for reserve{0,1}Adjusted, avoids stack too deep errors
            uint256 balance0Adjusted = balance0.mul(1000);
            uint256 balance1Adjusted = balance1.mul(1000);
            {
                // avoids stack too deep errors
                if (amount0In > 0) {
                    uint256 amount0InFee = amount0In.mul(swapFee);
                    balance0Adjusted = balance0Adjusted.sub(amount0InFee);
                    collectedFee0 = uint112(uint256(collectedFee0).add(amount0InFee));
                }
                if (amount1In > 0) {
                    uint256 amount1InFee = amount1In.mul(swapFee);
                    balance1Adjusted = balance1Adjusted.sub(amount1InFee);
                    collectedFee1 = uint112(uint256(collectedFee1).add(amount1InFee));
                }
                uint32 _tokenWeight0 = tokenWeight0; // gas savings
                if (_tokenWeight0 == 50) {
                    // gas savings for pair 50/50
                    require(balance0Adjusted.mul(balance1Adjusted) >= uint256(_reserve0).mul(_reserve1).mul(1000**2), "VLP: K");
                } else {
                    require(
                        IValueLiquidFormula(formula).ensureConstantValue(
                            uint256(_reserve0).mul(1000),
                            uint256(_reserve1).mul(1000),
                            balance0Adjusted,
                            balance1Adjusted,
                            _tokenWeight0
                        ),
                        "VLP: K"
                    );
                }
            }
        }
        _update(balance0, balance1, _reserve0, _reserve1);
        emit Swap(msg.sender, amount0In, amount1In, amount0Out, amount1Out, to);
    }

    // force balances to match reserves
    function skim(address to) external lock {
        address _token0 = token0; // gas savings
        address _token1 = token1; // gas savings
        _safeTransfer(_token0, to, IERC20(_token0).balanceOf(address(this)).sub(reserve0));
        _safeTransfer(_token1, to, IERC20(_token1).balanceOf(address(this)).sub(reserve1));
    }

    // force reserves to match balances
    function sync() external lock {
        _update(IERC20(token0).balanceOf(address(this)), IERC20(token1).balanceOf(address(this)), reserve0, reserve1);
    }
}

contract ValueLiquidFactory is IValueLiquidFactory {
    address public feeTo;
    address public formula;
    uint256 public protocolFee;
    address public feeToSetter;

    mapping(bytes32 => address) private _pairSalts;
    address[] public allPairs;
    mapping(address => uint64) private _pairs;

    constructor(address _feeToSetter, address _formula) public {
        feeToSetter = _feeToSetter;
        formula = _formula;
    }

    function isPair(address b) external view returns (bool) {
        return _pairs[b] > 0;
    }

    function allPairsLength() external view returns (uint256) {
        return allPairs.length;
    }

    function getPair(
        address tokenA,
        address tokenB,
        uint32 tokenWeightA,
        uint32 swapFee
    ) external view returns (address pair) {
        (address token0, address token1, uint32 tokenWeight0) = tokenA < tokenB ? (tokenA, tokenB, tokenWeightA) : (tokenB, tokenA, 100 - tokenWeightA);
        bytes32 salt = keccak256(abi.encodePacked(token0, token1, tokenWeight0, swapFee));
        pair = _pairSalts[salt];
    }

    function createPair(
        address tokenA,
        address tokenB,
        uint32 tokenWeightA,
        uint32 swapFee
    ) external returns (address pair) {
        require(tokenA != tokenB, "VLP: IDENTICAL_ADDRESSES");
        require(tokenWeightA >= 2 && tokenWeightA <= 98 && (tokenWeightA % 2) == 0, "VLP: INVALID_TOKEN_WEIGHT");
        // Minimum swap fee is 0.03%  & Maximum swap fee is 10%
        require(swapFee >= 3 && swapFee <= 100, "VLP: INVALID_SWAP_FEE");
        (address token0, address token1, uint32 tokenWeight0) = tokenA < tokenB ? (tokenA, tokenB, tokenWeightA) : (tokenB, tokenA, 100 - tokenWeightA);
        require(token0 != address(0), "VLP: ZERO_ADDRESS");
        // single check is sufficient
        bytes memory bytecode = type(ValueLiquidPair).creationCode;
        bytes32 salt = keccak256(abi.encodePacked(token0, token1, tokenWeight0, swapFee));
        require(_pairSalts[salt] == address(0), "VLP: PAIR_EXISTS");
        assembly {
            pair := create2(0, add(bytecode, 32), mload(bytecode), salt)
        }
        IValueLiquidPair(pair).initialize(token0, token1, tokenWeight0, swapFee);
        _pairSalts[salt] = address(pair);
        allPairs.push(pair);
        uint64 weightAndFee = uint64(swapFee);
        weightAndFee |= uint64(tokenWeight0) << 32;
        _pairs[address(pair)] = weightAndFee;
        emit PairCreated(token0, token1, pair, tokenWeight0, swapFee, allPairs.length);
    }

    function setFeeTo(address _feeTo) external {
        require(msg.sender == feeToSetter, "VLP: FORBIDDEN");
        feeTo = _feeTo;
    }

    function setFeeToSetter(address _feeToSetter) external {
        require(msg.sender == feeToSetter, "VLP: FORBIDDEN");
        feeToSetter = _feeToSetter;
    }

    function setProtocolFee(uint256 _protocolFee) external {
        require(msg.sender == feeToSetter, "VLP: FORBIDDEN");
        require(_protocolFee == 0 || (_protocolFee >= 2000 && _protocolFee <= 10000), "VLP: Invalid Protocol fee");
        protocolFee = _protocolFee;
    }

    function getWeightsAndSwapFee(address pair)
        public
        view
        returns (
            uint32 tokenWeight0,
            uint32 tokenWeight1,
            uint32 swapFee
        )
    {
        uint64 weightAndFee = _pairs[pair];
        if (weightAndFee > 0) {
            swapFee = uint32(weightAndFee);
            tokenWeight0 = uint32(weightAndFee >> 32);
            tokenWeight1 = 100 - tokenWeight0;
        } else {
            return (50, 50, 3);
        }
    }
}