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@krsnnik krsnnik/backwardsc.sol Secret
Created Jul 8, 2019

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/**
* @dev See `IERC20.transfer`.
*
* Unlike `send`, `recipient` is _not_ required to implement the `tokensReceived`
* interface if it is a contract.
*
* Also emits a `Sent` event.
*/
function transfer(address recipient, uint256 amount) external returns (bool) {
require(recipient != address(0), "ERC777: transfer to the zero address");
address from = msg.sender;
_callTokensToSend(from, from, recipient, amount, "", "");
_move(from, from, recipient, amount, "", "");
_callTokensReceived(from, from, recipient, amount, "", "", false);
return true;
}
/**
* @dev See `IERC20.allowance`.
*
* Note that operator and allowance concepts are orthogonal: operators may
* not have allowance, and accounts with allowance may not be operators
* themselves.
*/
function allowance(address holder, address spender) public view returns (uint256) {
return _allowances[holder][spender];
}
/**
* @dev See `IERC20.approve`.
*
* Note that accounts cannot have allowance issued by their operators.
*/
function approve(address spender, uint256 value) external returns (bool) {
address holder = msg.sender;
_approve(holder, spender, value);
return true;
}
function _approve(address holder, address spender, uint256 value) private {
// TODO: restore this require statement if this function becomes internal, or is called at a new callsite. It is
// currently unnecessary.
//require(holder != address(0), "ERC777: approve from the zero address");
require(spender != address(0), "ERC777: approve to the zero address");
_allowances[holder][spender] = value;
emit Approval(holder, spender, value);
}
/**
* @dev See `IERC20.transferFrom`.
*
* Note that operator and allowance concepts are orthogonal: operators cannot
* call `transferFrom` (unless they have allowance), and accounts with
* allowance cannot call `operatorSend` (unless they are operators).
*
* Emits `Sent`, `Transfer` and `Approval` events.
*/
function transferFrom(address holder, address recipient, uint256 amount) external returns (bool) {
require(recipient != address(0), "ERC777: transfer to the zero address");
require(holder != address(0), "ERC777: transfer from the zero address");
address spender = msg.sender;
_callTokensToSend(spender, holder, recipient, amount, "", "");
_move(spender, holder, recipient, amount, "", "");
_approve(holder, spender, _allowances[holder][spender].sub(amount));
_callTokensReceived(spender, holder, recipient, amount, "", "", false);
return true;
}
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