Gas Optimizations

[daopunk]

• using multiple if-revert statements is cheaper than using one long if-revert statement that uses && / ||.
• cache mapping lookups as function scoped variables rather than looking up the same mapping value multiple times in the same scope
• for function params, use calldata instead of memory when the function is not modifying the param

gas ops for for-loops:

• ++i is cheaper than i++
• after sol 0.8.0, can use unchecked to increment vars that have no risk of overflow
• cache the length in a var

example of most efficient solidity for-loop:

uint256 len = arr.length;
for (uint256 i; i < len) {
   unchecked { ++i }
   // logic
}