Multi-way Case Statement

[agate!spool.mu.edu!hri.com!noc.near.net!inmet!ryer@ucbvax.Berkeley.EDU ( Mike Ryer)]

Here's another way to get the affect of multi-way case:

  type Three_Cases is (F_F_F, F_F_T, F_T_F, F_T_T, 
                       T_F_F, T_F_T, T_T_F, T_T_T);

  Truth_Table: constant array (Boolean, Boolean, Boolean) of Three_Cases := 
       (((F_F_F, F_F_T), (F_T_F, F_T_T)), 
        ((T_F_F, T_F_T), (T_T_F, T_T_T)));
begin
    . . .

  case Truth_Table(a>b, c/=d, e<f) is
    when F_T_F | F_T_T => ...

    when T_T_F | T_F_F => ...

    when T_T_T => ...

    when others => ...

  end case;

Once you set up the two top declarations, you can code as many 3-way case
statements as you like, without repeating them.  I suspect that the ultimate
generated code is the same as what you would get if it were a built-in
language feature.

Mike Ryer
Intermetrics