Re: Data_Error and Enumeration_IO

[John McCormick <mccormick@cs.uni.edu>]

On Jan 12, 6:10 pm, "Randy Brukardt" <ra...@rrsoftware.com> wrote:
>
> Jeff and Georg already explained what is going on. But I have to admit I'm
> surprised that you aren't aware of this, since it has been a problem with
> Ada.Text_IO since the beginning of time (1980 in Ada's case).

Never be surprised about another's ignorance.  I wasn't in the Ada
world during the discussions in the 1980s.  The only thing in Jeff's
and Georg's notes of which I had not known was the reference to the
material on Data_Error and real types.  From that it seems that the
parsing of a potential floating point number uses knowledge of
previously entered characters.  For example, if you enter "1.2E." it
recognizes that the second decimal point is an error.  Yet when you
enter "abc" in my original example for enumeration IO, it cannot
recognize that no valid enumeration literal starts with an a.  It has
to process the entire identifier before it can see that. So the crux
of my question is why doesn't the consumption of characters for
enumeration input behave like that of real input. It doesn't really
matter other than to satisfy my curiosity.