Ethereum Cookbook

How to do it...

1. Consider the following basic token contract:

pragma solidity ^0.4.23;contract TokenContract {    mapping (address => uint) balances;    event Transfer(        address indexed _from,         address indexed _to,         uint256 _value    );    function sendToken(address receiver, uint amount)         public returns(bool) {        require(balances[msg.sender] < amount);        balances[msg.sender] -= amount;        balances[receiver] += amount;        emit Transfer(msg.sender, receiver, amount);        return true;    }    function getBalance(address addr) public view returns(uint) {        return balances[addr];    }}

2. It is a very common and simple token contract, which has functions to transfer tokens and to check the balance of each account.
3. At first glance, there is nothing in this contract that can possibly ...