Re: Getting GNAT to issue ARM error messages

[robert_dewar@my-dejanews.com]

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In article <7af1kj$pm7$1@platane.wanadoo.fr>,
  "Jean-Pierre Rosen" <rosen.adalog@wanadoo.fr> wrote:
> steve quinlan a �crit dans le message
<36C9C0BC.EA9C114E@lmco.com>...
> >I think I do remember him agreeing that the error
> >messages should use relevant RM terminology.

> THIS is a real issue. For example, my experience is that
> the term "subtype mark" is very confusing to beginners. I
> always have to explain that it means "the name of
> something that is a (sub)type".

I actually agree with JPR here, despite Steve's memory of
my agreeing to the contrary :-)

RM terminology, especially in RM 95, can often be quite
confusing, for example the value of a variable does not
include the tag, but an error message that depended on
the reader knowing the the use of the word "value" excluded
the tag, where this was critical to understanding, would
likely be confusing.

Similarly, a message that depended on the user knowing that
the term package excludes generic package could also be
confusing.

Almost everyone thinks of a package as having a spec and
a body, and insisting dogmatically on using package
declaration and subprogram declaration in all messages
might well be confusing.

Another example of terminology that could be confusing is
nominal subtype.

Actually what is really needed in some of the error
situations is not just a magic RM reference, or some
magic RM terminology to make things clear, but a long
and extended tutorial on a delicate point in the language.
I often write these tutorials, both here on CLA, and for
our customers! Elaboration issues for example are a
particularly tricky area.

Our vision for error messages is a tool for which we have
a nice name GNOME (GNat Online Message Explanation). The
idea is that you click on a message, and you get all kinds
of extra stuff, extra explanations, multiple RM references
with an explanation of how they apply (RM references
without this explanation are typically of limited value),
references to the Rationale, the AARM, and even to Ada text
books.

Unfortunately, the only thing that exists about this tool
right now is the name :-)

Actually in our experience, relatively few error messages
cause significant confusion at this stage (some of them are
ones for which we already have RM references, but they
still cause confusion!)


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