function balanceOf( address account ) public view virtual override returns (uint256) { return _balances[account]; } トークン(ERC20 )のコード解説 transfer (送信) function _transfer( address from, address to, uint256 amount ) internal virtual { uint256 fromBalance = _balances[from]; unchecked { _balances[from] = fromBalance - amount; _balances[to] += amount; } } リンク:https://github.com/OpenZeppelin/openzeppelin- contracts/blob/master/contracts/token/ERC20/ERC20.sol