def approve(ctx, _spender='address', _value='uint256', returns=STATUS):
        """ Standardized Contract API:
        function approve(address _spender, uint256 _value) returns (bool success)
        """
        ctx.allowances[ctx.msg_sender][_spender] += _value
        ctx.Approval(ctx.msg_sender, _spender, _value)
        return OK
Standardized Contract API:
        function approve(address _spender, uint256 _value) returns (bool success)