设计一个4位的算术逻辑单元

+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ ; Legal Partition Candidates ; +-----------+-------+----------------+--------------+----------------+--------+-----------------+---------------+-----------------+-------+----------------+--------------+------------------+-------------------+ ; Hierarchy ; Input ; Constant Input ; Unused Input ; Floating Input ; Output ; Constant Output ; Unused Output ; Floating Output ; Bidir ; Constant Bidir ; Unused Bidir ; Input only Bidir ; Output only Bidir ; +-----------+-------+----------------+--------------+----------------+--------+-----------------+---------------+-----------------+-------+----------------+--------------+------------------+-------------------+