Avoid repeated arithmetic operations in for loop can save gas

[code423n4]

Handle

WatchPug

Vulnerability details

https://github.com/code-423n4/2021-12-amun/blob/98f6e2ff91f5fcebc0489f5871183566feaec307/contracts/basket/contracts/facets/Basket/BasketFacet.sol#L158-L168

uint256 feeAmount = _amount.mul(bs.entryFee).div(10**18);

for (uint256 i; i < bs.tokens.length; i++) {
    IERC20 token = bs.tokens[i];
    uint256 tokenAmount =
        balance(address(token)).mul(_amount.add(feeAmount)).div(
            totalSupply
        );
    require(tokenAmount != 0, "AMOUNT_TOO_SMALL");
    token.safeTransferFrom(msg.sender, address(this), tokenAmount);
}

_amount.add(feeAmount) is being recalculated each in the for loop, which is unnecessary.

https://github.com/code-423n4/2021-12-amun/blob/98f6e2ff91f5fcebc0489f5871183566feaec307/contracts/basket/contracts/facets/Basket/BasketFacet.sol#L200-L213

uint256 feeAmount = _amount.mul(bs.exitFee).div(10**18);

for (uint256 i; i < bs.tokens.length; i++) {
    IERC20 token = bs.tokens[i];
    uint256 tokenBalance = balance(address(token));
    // redeem less tokens if there is an exit fee
    uint256 tokenAmount =
        tokenBalance.mul(_amount.sub(feeAmount)).div(totalSupply);
    require(
        tokenBalance.sub(tokenAmount) >= MIN_AMOUNT,
        "TOKEN_BALANCE_TOO_LOW"
    );
    token.safeTransfer(msg.sender, tokenAmount);
}

_amount.sub(feeAmount) is being recalculated each in the for loop, which is unnecessary and gas consuming.