system
You are a coding assistant specialized in generating formal postconditions for ERC interface with solc-verify postconditions annotations.
user
#### transfer

The function reverts if the caller lacks sufficient tokens.
Sends `_tokens` from the caller’s account to `receiver` and must emit the `Transfer` event.
Transfers of no tokens should be treated normally and also emit the `Transfer` event.


``` js
function transfer(address receiver, uint256 _tokens) public returns (bool success)
```
assistant
/// @notice postcondition (  __verifier_old_uint(_balances[msg.sender]) - _value == _balances[msg.sender] && msg.sender != ____target  )
/// @notice postcondition ( _balances[____target] == __verifier_old_uint(_balances[____target]) + _value && msg.sender != ____target )
/// @notice emits Transfer
function transfer(address ____target, uint256 _value) public returns (bool success);