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

Transfers `_value` amount of tokens from address `_from` to address `_to`, and MUST fire the `Transfer` event.

The `transferFrom` method is used for a withdraw workflow, allowing contracts to transfer tokens on your behalf.
This can be used for example to allow a contract to transfer tokens on your behalf and/or to charge fees in sub-currencies.
The function SHOULD `throw` unless the `_from` account has deliberately authorized the sender of the message via some mechanism.

*Note* Transfers of 0 values MUST be treated as normal transfers and fire the `Transfer` event.

``` js
function transferFrom(address _from, address _to, uint256 _value) public returns (bool success)
```
assistant
/// @notice postcondition (_balances[h] == __verifier_old_uint(_balances[h]) || ( __verifier_old_uint(_balances[h] ==  _balances[h] ) - t && h != r ) && h == r)
/// @notice postcondition ( _balances[r] == __verifier_old_uint(_balances[r]) + t && h != r ) || (_balances[r] == __verifier_old_uint(_balances[r]) && h == r)
/// @notice postcondition __verifier_old_uint(_allowed[h][msg.sender]) - t == _allowed[h][msg.sender]
function transferFrom(address h, address r, uint256 t) public returns (bool success);