Re: As-if Infinitely Ranged Integer Model

[Paolo Bonzini <bonzini at gnu dot org>]

On 07/27/2009 12:25 PM, Robert Dewar wrote:
> Laurent GUERBY wrote:
>
> > > > if Dynamic_N >= T'First and Dynamic_N > T'Last then
> > > Huh? I can't understand the first comparison.
> > > Actually Ada is not Fortran-66 and allows empty loops, no?
> >
> > Ada for loop over "A .. B" will be empty if "A > B" and we obviously
> > must not raise an exception if the loop is empty hence the first
> > comparison is equivalent to "not (T'First > Dynamic_N)" which is true
> > when the loop is not empty.
>
> GNAT does not do this kind of hoisting, though this particular case
> could be fiddled in the front end.

I suppose though that in Ada Dynamic_N will often be a subtype of T, at 
which point the hoisting is pointless because you know that the check 
passes.

Paolo