Re: NVRAM or how can I enforce a range check in Ada83.

[bobduff@world.std.com (Robert A Duff)]

In article <dewar.848229223@merv>, Robert Dewar <dewar@merv.cs.nyu.edu> wrote:
>As for requirements, there is not even a requirement that error messages
>be generated for illegal programs, since again messages are entirely outside
>the language definition. ...

This is not right.  1.1.3(1,4) say, "A conforming implementation shall
... Identify all programs or program units that contain errors ...".
Well, to me, that seems to imply that the implementation has to give
some indication on errors -- I would call that an "error message".

Of course, there is no requirement that the error message be useful.  It
could say, "This program is illegal."  (It would be friendlier to say
why, and give a line number or something.)  It could even just "beep" to
indicate an error.  But if the implementation were completely silent
about errors -- i.e. gave identical output for errors and non-errors, I
would say that clearly violates the above requirement.

>... The only semantic requirement is that the library
>(Ada 83) or compilation environment (Ada 95) not be affected by compiling
>an illegal unit.

Not true for Ada 95.  In Ada 95 it *is* permissible for the compilation
of an illegal compilation unit to affect the compilation environment.
The only requirement is that you can't run an illegal or inconsistent
partition.

- Bob