Gas Optimizations

[code423n4]

[G-01] ++i costs less gas than i++, especially when it's used in for loops (same for ++j vs j++)

Instances include: https://github.com/code-423n4/2022-07-swivel/blob/daf72892d8a8d6eaa43b9e7d1924ccb0e612ee3c/Swivel/Swivel.sol#L100 https://github.com/code-423n4/2022-07-swivel/blob/daf72892d8a8d6eaa43b9e7d1924ccb0e612ee3c/Swivel/Swivel.sol#L269 https://github.com/code-423n4/2022-07-swivel/blob/daf72892d8a8d6eaa43b9e7d1924ccb0e612ee3c/Swivel/Swivel.sol#L418 https://github.com/code-423n4/2022-07-swivel/blob/daf72892d8a8d6eaa43b9e7d1924ccb0e612ee3c/Swivel/Swivel.sol#L564

[G-02] calldata instead of memory for read-only function parameter If a reference type function parameter is read-only, it is cheaper in gas to use calldata instead of memory. Calldata is a non-modifiable, non-persistent area where function arguments are stored, and behaves mostly like memory. Try to use calldata as a data location because it will avoid copies and also makes sure that the data cannot be modified.

Instances include: https://github.com/code-423n4/2022-07-swivel/blob/daf72892d8a8d6eaa43b9e7d1924ccb0e612ee3c/Swivel/Swivel.sol#L495 https://github.com/code-423n4/2022-07-swivel/blob/daf72892d8a8d6eaa43b9e7d1924ccb0e612ee3c/Marketplace/MarketPlace.sol#L68 https://github.com/code-423n4/2022-07-swivel/blob/daf72892d8a8d6eaa43b9e7d1924ccb0e612ee3c/Marketplace/MarketPlace.sol#L69 https://github.com/code-423n4/2022-07-swivel/blob/daf72892d8a8d6eaa43b9e7d1924ccb0e612ee3c/Creator/Creator.sol#L36 https://github.com/code-423n4/2022-07-swivel/blob/daf72892d8a8d6eaa43b9e7d1924ccb0e612ee3c/Creator/Creator.sol#L37

[G-03] += costs more gas than = + for state variables (also -= vs = - )

Instances include: https://github.com/code-423n4/2022-07-swivel/blob/daf72892d8a8d6eaa43b9e7d1924ccb0e612ee3c/Swivel/Swivel.sol#L121 https://github.com/code-423n4/2022-07-swivel/blob/daf72892d8a8d6eaa43b9e7d1924ccb0e612ee3c/Swivel/Swivel.sol#L158 https://github.com/code-423n4/2022-07-swivel/blob/daf72892d8a8d6eaa43b9e7d1924ccb0e612ee3c/Swivel/Swivel.sol#L121 https://github.com/code-423n4/2022-07-swivel/blob/daf72892d8a8d6eaa43b9e7d1924ccb0e612ee3c/Swivel/Swivel.sol#L222 https://github.com/code-423n4/2022-07-swivel/blob/daf72892d8a8d6eaa43b9e7d1924ccb0e612ee3c/Swivel/Swivel.sol#L287 https://github.com/code-423n4/2022-07-swivel/blob/daf72892d8a8d6eaa43b9e7d1924ccb0e612ee3c/Swivel/Swivel.sol#L318 https://github.com/code-423n4/2022-07-swivel/blob/daf72892d8a8d6eaa43b9e7d1924ccb0e612ee3c/Swivel/Swivel.sol#L348 https://github.com/code-423n4/2022-07-swivel/blob/daf72892d8a8d6eaa43b9e7d1924ccb0e612ee3c/Swivel/Swivel.sol#L383 https://github.com/code-423n4/2022-07-swivel/blob/daf72892d8a8d6eaa43b9e7d1924ccb0e612ee3c/VaultTracker/VaultTracker.sol#L67 https://github.com/code-423n4/2022-07-swivel/blob/daf72892d8a8d6eaa43b9e7d1924ccb0e612ee3c/VaultTracker/VaultTracker.sol#L68 https://github.com/code-423n4/2022-07-swivel/blob/daf72892d8a8d6eaa43b9e7d1924ccb0e612ee3c/VaultTracker/VaultTracker.sol#L102 https://github.com/code-423n4/2022-07-swivel/blob/daf72892d8a8d6eaa43b9e7d1924ccb0e612ee3c/VaultTracker/VaultTracker.sol#L174 https://github.com/code-423n4/2022-07-swivel/blob/daf72892d8a8d6eaa43b9e7d1924ccb0e612ee3c/VaultTracker/VaultTracker.sol#L193 https://github.com/code-423n4/2022-07-swivel/blob/daf72892d8a8d6eaa43b9e7d1924ccb0e612ee3c/VaultTracker/VaultTracker.sol#L194 https://github.com/code-423n4/2022-07-swivel/blob/daf72892d8a8d6eaa43b9e7d1924ccb0e612ee3c/VaultTracker/VaultTracker.sol#L230 https://github.com/code-423n4/2022-07-swivel/blob/daf72892d8a8d6eaa43b9e7d1924ccb0e612ee3c/VaultTracker/VaultTracker.sol#L234

[G-04] Using private rather than public for constants saves gas If needed, the value can be read from the verified contract source code. Savings are due to the compiler not having to create non-payable getter functions for deployment calldata, and not adding another entry to the method ID table.

Instances include: https://github.com/code-423n4/2022-07-swivel/blob/daf72892d8a8d6eaa43b9e7d1924ccb0e612ee3c/Swivel/Swivel.sol#L25 https://github.com/code-423n4/2022-07-swivel/blob/daf72892d8a8d6eaa43b9e7d1924ccb0e612ee3c/Swivel/Swivel.sol#L26 https://github.com/code-423n4/2022-07-swivel/blob/daf72892d8a8d6eaa43b9e7d1924ccb0e612ee3c/Swivel/Swivel.sol#L27 https://github.com/code-423n4/2022-07-swivel/blob/daf72892d8a8d6eaa43b9e7d1924ccb0e612ee3c/Swivel/Swivel.sol#L35

[robrobbins]

++ addressed: https://github.com/Swivel-Finance/gost/pull/428

[robrobbins]

+= = -= addressed https://github.com/Swivel-Finance/gost/pull/429

not switching CONST to private as they are often queried from dapps / fe