Re: Tables vs functions (was Re: Anonymous array clarification.)

["Marin David Condic" <dont.bother.mcondic.auntie.spam@[acm.org>]

Or as an alternative:

> function Tomorrow(A_Day : in Day) return Day is
> begin
>   return Day'Succ(A_Day);
  exception
    when Constraint_Error =>
        return Day'First ;
> end Tomorrow;

There is, of course, going to be some debate about using exceptions for
conditions you expect to happen. However, I'd point out that the code is a
bit more brief and that in some implementations it might be (on the average)
faster - for whatever that's worth. Its just an alternate implementation
style. :-)

Which would I personally use? I'd usually go with what you described. There
may be occasional uses of the Constraint_Error trap in things I write of
this nature - I'm partial to that technique when implementing saturated
arithmetic. Dunno if there is any consensus that it should be one way or
another in this case - but its a good one to put in a programming style
guideline. Like formatting rules, I'd go with whatever the style guide
recommends for a given project.

MDC
--
Marin David Condic
Senior Software Engineer
Pace Micro Technology Americas    www.pacemicro.com
Enabling the digital revolution
e-Mail:    marin.condic@pacemicro.com
Web:      http://www.mcondic.com/


"Ray Blaak" <blaak@infomatch.com> wrote in message
news:un14uy8v0.fsf_-_@infomatch.com...
>
> Hmm.
>
> function Tomorrow(A_Day : in Day) return Day is
>   Result : Day;
> begin
>   if A_Day < A_Day'Last then
>     Result := Day'Succ(A_Day);
>   else
>     Result := Day'First;
>   end if;
>   return Result;
> end Tomorrow;
>
> Doesn't seem too complicated, looks the same to the user, is just as time
> efficient, is more space efficient, and works for any size of
> array/enumeration type.
>
> It also is more robust, since one does not have to tediously type out the
> items in a possibly erroneous way.
>
> On the other hand, tables are useful when the calculations are expensive,
> difficult or tedious to describe algorithmically, or the values change
> according to subsequent data inputs.
>
> --
> Cheers,                                        The Rhythm is around me,
>                                                The Rhythm has control.
> Ray Blaak                                      The Rhythm is inside me,
> blaak@infomatch.com                            The Rhythm has my soul.