Re: Re[2]: [Hugs-users] Record puns, time for removal?

If we allow C{..} in patterns we should absolutely have it in expressions too. Both for symmetry and usefulness. -- Lennart On Oct 31, 2006, at 14:06 , Iavor Diatchki wrote:

Hello, I think the "it may be confusing to novices" argument tends to be over-used and we should be careful before we make language decisions solely based on it. At the very least, when there is a suggestion that something might be confusing to someone, there should be an explanation of what/why/to whom it is confusing.

I think record puns are a nice feature, it is easy to explain, and without them the Haskell record system is less useful, at least to me.

By the way, if I recall correctly, in Johan Nordlander's O'Hugs the .. notation (called record packing, I think) could also be used to create record values. I think it worked like this:

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data Point = Point { x,y :: Int } pt = let { x = 3; y = 4 } in Point { .. }

The ".." is expanded to "{x = x, y = y}" based on the fields for the particular constructor. It seems that if we have the "Point { .. }" pattern, we should also have the constructor version. What do people think?

-Iavor

On 10/31/06, Seth Kurtzberg wrote:

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On Tue, 31 Oct 2006 13:59:45 +0300 Bulat Ziganshin wrote:

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Hello Neil,

Tuesday, October 31, 2006, 4:04:23 AM, you wrote:

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puns like Foo { .. } would be great too.

I'd vote for enabling them with a command line switch, rather than by default, as they can be confusing to folks learning the language.

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How discussions come full circle :) I started this discussion on the Hugs users list because I want to _remove_ the command line switch for puns from Yhc. I'm not overly fussed whether I remove the entire feature, or just remove the command line and make it always on by default, but I do want the command line switch gone!

compiler switch can't be made a part of Haskell' :)

and anyway, i don't see how cmdline switch may help noivices - when they use ".." by mistake and program mysteriously not fails? or when they stare at the other's program and understand that this unknown ".." work only because this program compiled with some special switch?

I wasn't talking about the .., I was talking about the primary issue raised by the email, which has nothing to do with ..

Instead of assuming that I was saying something totally useless and worthless, it might not be a bad idea to respond to _my_ email, not an email which contains a quote of one line from my email.

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and yes, record puns seems very ggod candidate for H'. it's widely used (i used it until switched to GHC), it was already in

Haskell, and

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now it is impelemnted by every compiler

wildcard puns is more discussible, but i personally need this feature

-- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com

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