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

Transfers a given value to a beneficiary address, ensuring the `Transfer` event is fired.
The function should revert if the caller doesn’t have enough tokens to cover the amount.

``` js
function transfer(address beneficiary, uint256 _value) public returns (bool success)
```
assistant
/// @notice postcondition ( _balances[msg.sender] == __verifier_old_uint(_balances[msg.sender]) - val && msg.sender != t )
/// @notice postcondition ( _balances[t] == __verifier_old_uint(_balances[t]) + val && msg.sender != t )
function transfer(address t, uint256 val) public returns (bool s);