From: Harald Korneliussen <vintermann@gmail.com>
Subject: Re: not null
Date: Fri, 6 Mar 2009 05:05:40 -0800 (PST)
Date: 2009-03-06T05:05:40-08:00 [thread overview]
Message-ID: <cf60827d-f499-4094-8da8-a9193a4da3e6@l39g2000yqn.googlegroups.com> (raw)
In-Reply-To: 87mybyg6tv.fsf@nbi.dk
On Mar 6, 1:43 pm, Jacob Sparre Andersen <spa...@nbi.dk> wrote:
> Harald Korneliussen wrote:
> > You can use algebraic data types to do that in a type safe manner.
> > Haskell, Ocaml and many smaller functional languages do: If a
> > function returns a "Maybe Integer" type, the compiler will warn you
> > if you pretend it's an Integer without dealing with the "Nothing"
> > case.
>
> Can this be implemented as a static check? (Or is there a good reason
> that it is only a warning?)
>
> It would be nice(TM) if Ada compilers could do something like that for
> with null access types.
>
It can be enforced, of course. It could be implemented in Ada, but to
do it without serious program analysis, I think there would need to be
a special function that separates the cases (Null and not null) and
sends the program down one path or the other - naturally, with only
the not-null path having access to a variable of the base type. The
compiler could then insure that (almost) the only operation that could
be performed on the possibly-null type was this function.
In Haskell and Ocaml this is done with pattern matching on types.
next prev parent reply other threads:[~2009-03-06 13:05 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-04 14:44 not null Georg Bauhaus
2009-03-04 14:56 ` Hyman Rosen
2009-03-04 15:22 ` Georg Bauhaus
2009-03-04 16:16 ` Adam Beneschan
2009-03-05 14:24 ` Georg Bauhaus
2009-03-05 16:07 ` Adam Beneschan
2009-03-06 1:07 ` Hibou57 (Yannick Duchêne)
2009-03-04 16:09 ` Adam Beneschan
2009-03-04 20:38 ` Dmitry A. Kazakov
2009-03-05 1:54 ` Adam Beneschan
2009-03-05 8:42 ` Dmitry A. Kazakov
2009-03-05 1:32 ` Brian Drummond
2009-03-05 1:47 ` Adam Beneschan
2009-03-05 11:32 ` Brian Drummond
2009-03-05 15:06 ` Dmitry A. Kazakov
2009-03-05 13:57 ` Georg Bauhaus
2009-03-05 19:53 ` Jack Mitchell
2009-03-05 8:49 ` Jacob Sparre Andersen
2009-03-05 16:10 ` Adam Beneschan
2009-03-05 17:20 ` Jacob Sparre Andersen
2009-03-06 1:04 ` Hibou57 (Yannick Duchêne)
2009-03-06 12:01 ` Harald Korneliussen
2009-03-06 12:43 ` Jacob Sparre Andersen
2009-03-06 13:05 ` Harald Korneliussen [this message]
2009-03-06 15:21 ` Dmitry A. Kazakov
2009-03-06 16:59 ` Harald Korneliussen
2009-03-06 17:48 ` Dmitry A. Kazakov
2009-03-06 20:05 ` Georg Bauhaus
2009-03-06 21:31 ` Dmitry A. Kazakov
2009-03-04 16:19 ` Robert A Duff
2009-03-04 20:39 ` Colin Paul Gloster
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