Re: Suggestion for multivalue boolean case for 9X

[darwin.sura.net!spool.mu.edu!umn.edu!The-Star.honeywell.com!saifr00.cfsat .honeywell.com!dunbar@gatech.edu (Mark Dunbar)]

In article <dnsurber.724028252@node_26400> dnsurber@lescsse.jsc.nasa.gov (Dougl
as N. Surber) writes:
>How many times have you seen code like the following:
>
>    if cond_1 then
>        if cond_2
>	    if cond_3 then
>		s_t_t_t;
>	    else
>		s_t_t_f;
>	    end if;
>	else
>	    if cond_3 then
>		s_t_f_t;
>	    else
>		s_t_f_f;
>	    end if;
>	end if;

      [etc]...

>I find this hard to read and even harder to maintain.  Cond_3 appears
>four times.  That's a maintenance nightmare.  A case statement that
>worked on arrays of booleans would be a big improvement.  Something like
>the following:
>
>    case (cond_1, cond_2, cond_3) is
>	when (true,  true,  true ) =>
>	    s_t_t_t;
>	when (true,  true,  false) =>
>	    s_t_t_f;
>	when (true,  false, true ) =>
>	    s_t_f_t;
>	when (true,  false, false) =>
>	    s_t_f_f;

	[etc]...
>
>Douglas Surber
>Lockheed
>Houston, TX
>
Using Ada83, instead of the nested if statement, one could do the following:

  if    ( not Cond_1 ) and ( not Cond_2 ) and ( not Cond_3 ) then
    ...
  elsif ( not Cond_1 ) and ( not Cond_2 ) and (     Cond_3 ) then
    ...
  elsif ( not Cond_1 ) and (     Cond_2 ) and ( not Cond_3 ) then
    ...
  elsif ( not Cond_1 ) and (     Cond_2 ) and (     Cond_3 ) then
    ...
  elsif (     Cond_1 ) and ( not Cond_2 ) and ( not Cond_3 ) then
    ...

  etc.

Although I do agree the case statement would be more elegant (sp?) and
potentially faster if there were enough branches to cancel out the
overhead of a case.