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UNDER THE FLOW

The devs have told you that the standard ERC20 implementation wastes lots of gas with unnecessary events, storage reads and writes, and other inefficiencies. They have developed an improved version of the standard ERC20 contract called ImprovedERC20 that saves gas by removing these inefficiencies and doing only the important checks.

WINNING CONDITION

Get a token balance.

▾src

ImprovedERC20.sol

▸interfaces

▸script

pragma solidity ^0.7.0;

import {IImprovedERC20} from "./interfaces/IImprovedERC20.sol";

contract ImprovedERC20 is IImprovedERC20 {
    mapping(address => uint256) public override balanceOf;
    mapping(address => mapping(address => uint256)) public override allowance;
    address public override owner;

    string public override name;
    string public override symbol;
    uint8 public override decimals;

    constructor(
        string memory _name,
        string memory _symbol,
        uint8 _decimals,
        uint256 _initialSupply
    ) {
        name = _name;
        symbol = _symbol;
        decimals = _decimals;
        owner = msg.sender;
        balanceOf[msg.sender] = _initialSupply;
    }

    function transfer(
        address _to,
        uint256 _value
    ) external override returns (bool) {
        require(balanceOf[msg.sender] >= _value, "Insufficient balance");
        balanceOf[msg.sender] -= _value;
        balanceOf[_to] += _value;
        return true;
    }

    function transferFrom(
        address _from,
        address _to,
        uint256 _value
    ) external override returns (bool) {
        require(balanceOf[_from] >= _value, "Insufficient balance");
        require(
            allowance[_from][msg.sender] - _value > 0,
            "Insufficient allowance"
        );
        balanceOf[_from] -= _value;
        balanceOf[_to] += _value;
        allowance[_from][msg.sender] -= _value;
        return true;
    }

    function approve(
        address _spender,
        uint256 _value
    ) external override returns (bool) {
        allowance[msg.sender][_spender] = _value;
        return true;
    }

    function mint(uint256 _value) external override {
        require(msg.sender == owner, "Only owner can mint");
        balanceOf[msg.sender] += _value;
    }

    function burn(address _who, uint256 _value) external override {
        require(balanceOf[_who] >= _value, "Insufficient balance");
        balanceOf[_who] -= _value;
    }
}