Re: Curry module system

From: Bernd Brassel <>
Date: Mon, 27 Feb 2006 15:16:00 +0100

Claus Reinke wrote:
> does Curry have type classes?

No, Curry does not support type classes. This is exactly the point where
I feel that any more substantial record system is much more effort than
we can cope with just now. Just like what you said:

> as long as implementation effort is non-trivial,
> the limited developer resources are not going to be invested on new
> records unless there is a good chance that those new records will be
> the last records for some time to come!-)

is especially true about Curry. But the paper you mention might be a
good option. Incidently, I already had a lock at it, because it was the
most recent addition to the topic. But I did not realize that the
approach would work without type classes.

> if not, that is no option, but you might
> want to look into Daan Leijen's TFP 2005 paper "Extensible records with
> scoped labels"

I didn't realize that the wide use of the haskell98 version might have
been part of the problem as you suggest:

> what was not expected was that now there are lots of programs using
> these pseudo-records, so further experimentation to get beyond this
> gap-filling interim solution has ground to a halt so as to avoid breaking existing code..

So, maybe we can avoid this pitfall by implementing (for now) only part
of a more expressive approach? This would keep Curry extensible for the
better solution (maybe as soon as we have type classes), but would also
give us the possibility of programming with records, even when they are
not yet extensible.

Have a nice Curry!

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Received on Mo Feb 27 2006 - 15:46:57 CET

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