    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.
File: /contracts/MerkleDropFactory.sol   #1

29       mapping (address => mapping (uint => bool)) public withdrawn;
File: /contracts/MerkleResistor.sol   #2

50       mapping (address => mapping (uint => bool)) public initialized;
File: /contracts/MerkleVesting.sol   #3

38       mapping (address => mapping (uint => bool)) public initialized;
File: /contracts/VoterID.sol   #4

21       mapping (address => mapping (address => bool)) public operatorApprovals;
