interface ISavingsContractV2 {
    // DEPRECATED but still backwards compatible
    function redeem(uint256 _amount) external returns (uint256 massetReturned);

    function creditBalances(address) external view returns (uint256); // V1 & V2 (use balanceOf)

    // --------------------------------------------

    function depositInterest(uint256 _amount) external; // V1 & V2

    function depositSavings(uint256 _amount) external returns (uint256 creditsIssued); // V1 & V2

    function depositSavings(uint256 _amount, address _beneficiary)
        external
        returns (uint256 creditsIssued); // V2

    function redeemCredits(uint256 _amount) external returns (uint256 underlyingReturned); // V2

    function redeemUnderlying(uint256 _amount) external returns (uint256 creditsBurned); // V2

    function exchangeRate() external view returns (uint256); // V1 & V2

    function balanceOfUnderlying(address _user) external view returns (uint256 balance); // V2

    function underlyingToCredits(uint256 _credits) external view returns (uint256 underlying); // V2

    function creditsToUnderlying(uint256 _underlying) external view returns (uint256 credits); // V2
}
function balanceOfUnderlying(address _user) external view returns (uint256 balance); // V2

// V1 & V2