Re: newbie can't get exceptions to work!

[Laurent Guerby <guerby@acm.org>]

Brian Rogoff <bpr@shell5.ba.best.com> writes:
> You should know that nothing is obvious when you're discussing the
> OCaml type system :-). OK, that's not fair. It is obvious when
> considered in the context of mathematically sound type systems. If
> you're not well versed in the theory of such type systems, simple
> explanations won't be helpful.  Check the caml-list for the mail of
> the past few weeks titled "The Future of Labels" or somesuch.

I'm not super-versed in those things (I've read a whole bunch of
papers and FP conference proeedings over the years but never
implemented anything), but as I see it, raw labeled arguments
are a near syntactic feature. Let's say you have:

f x y = x + y

Then either you don't use labels

z = f 2 3

or you use them for all args

z = f (y => 3, x => 2)

The compiler finds out the special => syntax, looks up for a matching
function name and labels, and then just reorders according to declaration

z = f 3 2

And you're back to the regular thing (you need to be a bit smart in
your match to handle currying, but you can drop that if it's too much
of a problem). If the labeled syntax can be recognized without too
much fuss, it won't interfere at all with the regular type analysis
since it will be separate prior pass.

> Which idiotic platforms?

All commercial UNIXes (AIX, IRIX, Solaris, OSF1) and VMS, plus NT, all
with threading correctly supported.

> I believe you made the right decision. It was a brave one too, since
> I bet there was a strong push for C++. Ada would be my choice too,
> given what you told me.

I didn't tell you the major thing ;-), namely that most of the team
writing the software are not trained software engineers but financial
and numerical people. C/C++ is just suicide in this environment (no
array bound checking, pointers all over the place, awful error
messages and brain-dead syntax...). I spent one whole year of my life
chasing out of bound access, memory management errors and random hard
to find crashes in a >500KSLOC of C software with crapping debugging
technology (Visual C++ released compiled software bugs usually go away
when you compile in debug mode, I still don't know how people tolerate
this...), I think this qualifies me for having an opinion on the topic
;-).

As for the strong push for C++, that was everyone but two people, but
management did trust us and choosed Ada after three monthes of
reflexion.  Now the C++ people are all saying C++ is legacy and doing
Java, and Java people are right now wondering about C#... Needless to
say their technology opinion is now 0 weighted as far as my management
is concerned. The software survived one merger, introduction of
distributed computations, growth of the team and is greatly satisfying
to business.

But even if written in Ada, the code keeps FP-like technique like
being stateless, having non mutable objects and provably not leaking
reference counting GC scheme (no cycles can be created with non
mutable objects).

> I trust the support has been good? 

Ups and downs, but our bugs do get fixed, our technical questions
about use of the technology get excellent and timely answer, and the
GNAT technology is definitely evolving in the right direction over the
years (new tools, new platforms).

Talking about support in the software tool business is kinda tricky,
for example I know about no other tools used here where users get
fixes from the vendor at all except at the mandatory update to new
versions.

Aren't you worried about lack of formal support for OCaml in your
company?

-- 
Laurent Guerby <guerby@acm.org>