Swivel v3 contest - ElKu's results

1) Missing natspec comment.

1. ZcToken.sol 1. There is no natspec comment for parameter holder in withdraw function. 2. There is no natspec comment for parameter holder in redeem function.

2) Declare magic numbers as constants in VaultTracker.sol

Magic number 1e26 used in 6 functions: addNotional, removeNotional, redeemInterest, transferNotionalFrom, transferNotionalFee and removeNotional.

1) State variables which are read more than once should be cached to save gas.

1. ZcToken.sol 1. protocol, redeemer and maturity state variables in convertToUnderlying function. 2. protocol, redeemer and maturity state variables in convertToPrincipal function.

2) Remove Identical functions in ZcToken.sol.

1. convertToUnderlying and previewRedeem functions are identical.
2. convertToPrincipal and previewWithdraw functions are identical.

3) Convert frequenctly used revert checks into a modifier.

ZcToken.sol has the following revert check which repeats twice.

if (block.timestamp < maturity) {
            revert Maturity(maturity);
        }

4) Simplify formula for better readability and gas saving.

There are 6 functions in VaultTracker.sol ( addNotional, removeNotional, redeemInterest, transferNotionalFrom, transferNotionalFee and removeNotional ) which calculate interest in the following way:

      if (maturityRate > 0) { 
        // calculate marginal interest
          yield = ((maturityRate * 1e26) / sVault.exchangeRate) - 1e26;
      } else {
          yield = ((exchangeRate * 1e26) / sVault.exchangeRate) - 1e26;
      }
      uint256 interest = (yield * sVault.notional) / 1e26;

These can be re-written as below:

      if (maturityRate > 0) { 
        // calculate marginal interest
          interest = ((maturityRate * sVault.notional - sVault.notional) / sVault.exchangeRate);
      } else {
          interest = ((exchangeRate * sVault.notional - sVault.notional) / sVault.exchangeRate);
      }

5) Use already cached variable instead of indexing again.

There are two instances of this:

1. The value of o[i] is already cached into memory variable order. So use it inside the following if-else statements instead of freshly indexing again.
2. The same is happening in the exit function.