Re: Enumeration representation enhancement proposal

[Jacob Sparre Andersen <sparre@nbi.dk>]

Wojtek Narczynski wrote:

> >> Maybe this could be improved in Ada 2005? For example:
> >> 
> >> type Mix_Code is (Red, Green, Blue, Grey);
> >> 
> >> --  Modest proposal
> >> 
> >> for Mix_Code use (Red => 1, Green => 2, Blue => 3, Grey => others);
> >> 
> >> This should be relatively straightforward to implement, and would
> >> cover most needs.
> > 
> > The problem with this proposal it that (actual) values of the type
> > would no longer satisfy the ordering criteria (that a machine < or
> > > test will always have the same result as the corresponding
> > canonical test).
> 
> I don't follow, could you provide a sample Ada code which would be
> problematic?

  for Colours use (Red => 1, Green => 2, Blue => 4, Muddy => others);

  if Muddy < Blue then
     --  Do we ever get here?  Both 3 and 5 represents Muddy.  The one
     --  is smaller than 4 (which represents Blue), the other one
     --  isn't.  end if;
  end if;

Greetings,

Jacob
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