JGcarv

pragma solidity 0.4.24;

contract SecretVariable {

  uint256 secret;
  uint256 public guess;

  constructor(uint256 _secret) {
    secret = _secret;
  }

JGcarv

pragma solidity 0.4.24;

interface IERC20 {
  function totalSupply() external view returns (uint256);
  function balanceOf(address who) external view returns (uint256);
  function transfer(address to, uint256 value) external returns (bool);
  function transferFrom(address from, address to, uint256 value) external returns (bool);
}

contract ERC20Exchange {

JGcarv

pragma solidity 0.4.21;

import "./Utils/SafeMath.sol";

contract ExampleToken{

    using SafeMath for uint256;

    event Transfer(address indexed _from, address indexed _to, uint256 _value);
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);