pragma solidity ^0.4.21; pragma experimental ABIEncoderV2; contract Metacoin { mapping (address => uint) public balances; event Transfer(address indexed _from, address indexed _to, uint256 _value); struct TransferData { address to; uint256 amount; } struct NestedTransferData { TransferData transferData; uint32 callback; } function Metacoin() public { balances[msg.sender] = 10000; } function transfer(TransferData transferData) public returns (bool success) { if (balances[msg.sender] < transferData.amount) return false; balances[msg.sender] -= transferData.amount; balances[transferData.to] += transferData.amount; Transfer(msg.sender, transferData.to, transferData.amount); return true; } function transfer(TransferData transferData, uint32 callback) public returns (int) { transfer(transferData); return callback; } function transfer(NestedTransferData nestedTransferData) public returns (int) { return transfer(nestedTransferData.transferData, nestedTransferData.callback); } }