Re: C getchar() functionality in Ada

[Adam Beneschan <adam@irvine.com>]

On Feb 17, 12:24 pm, Hyman Rosen <hyro...@mail.com> wrote:
> Thomas Locke wrote:
> > But I understand what you're saying: No end of line characters in Ada!
> > Except perhaps when using Get_Immediate and Look_Ahead?
>
> The Ada design has the same error here as Pascal did.
> End of Line and End of File are like a craps table;
> you can know whether the table *was* hot or cold, but
> you cannot know whether the table *will be* hot or
> cold. Similarly, you cannot know whether you are at
> end of line or end of file until you have tried reading
> a character. Ada pretends otherwise, but behind the
> scenes it's doing a secret character read-ahead, which
> is what causes the odd behavior.
>
> I speak about the various modern OSes. Presumably, once
> upon a time input was such that this paradigm made sense,
> just like Fortran had special output formatting characters
> to rotate the roll of paper.

I'm not sure if you're implying that VMS is one of those OS's that are
as outdated as Fortran's formatting characters and horse-drawn
carriages, but when Ada's Text_IO package was designed, VMS was a big
thing.  And VMS text files do not (or didn't) have end-of-line
"characters".  They weren't organized just as amorphous streams of
bytes as they are on Unix-like systems and on Windows, but the OS
itself structured the files into lines.  Ada was designed to be
portable, so in that context I don't think its design was a mistake; a
design that relied on text files to be viewed as having "characters"
to separate lines, pages, etc., *would* probably have been a mistake,
when the goal of portability is kept in mind.

                                -- Adam