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Question on language design (keywords vs Pervasives)
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Date: 2000-08-21 (21:42)
From: Pierre Weis <Pierre.Weis@i...>
Subject: Re: Question on language design (keywords vs Pervasives)
> >>>>> "pw" == Pierre Weis <> writes:
>     pw> You're right, there is no really good example that uses
>     pw> redefinition of raise. That's why the advantage to be able to
>     pw> redefine it may overcome the inconvenience of not being always
>     pw> sure of its meaning.
> Actually, I just thought of one.  :) If you redefine raise in a
> special way, you could have it report that it was raising exceptions,
> even if those exceptions are later caught.  Might be good for
> analyzing your code.

Mm. I don't think it could be considered ``good for analyzing your
code'' if you compare to real tools such as the replay debugger
(dynamic analysis) or Francois Pessaux's exception analyzer (static

>     pw> You're right, we don't want to have zillions of keywords. On
>     pw> the other hand, you also need to have some level of confidence
>     pw> into the words you use in the language, otherwise you can
>     pw> write horrors as the famous
>     pw> if else then else else then
>     pw> when then and else are not reserved.
> Right.  But I don't think this is necessarily the case for raise.  I
> just gave a good example above.  There's also the possibility of
> somebody who could really care less about raising exceptions most of
> the time (e.g. me) but who has some code which performs an operation
> named "raise".  In that context, having to fight the system to get
> around it is bad.

But reading code that uses ``raise'' all over the place to do many
things other than raising exceptions could also be extreamely

> There's always a tension here.  For example, when I'm writing PL
> implementations, the fact that "type" is a keyword is rather
> upsetting.  But, I can deal--especially because I know that O'Caml
> doesn't have that many gratuitous keywords--everything's there for a
> reason.
> John.

Exactly, that's why I explained the reasons why we used to have raise
as a keyword, just to get a cleaner language: nothing gratuitous here,
the notion of exception raising is considered important and worth a
keyword to handle them (try) and a keyword to throw them (raise).

Pierre Weis

INRIA, Projet Cristal,,