Call for Nominations: Haskell Prime language committee
Dear Haskell lovers, The Haskell Prime process for standardisation of new versions of the Haskell language is at something of an impasse. Since the Haskell 2010 Report was issued (at the end of 2009), there has been very little momentum to formalise existing extensions and generalisations, nor appetite to decide on whether any such extensions should be adopted as part of the core language standard. We therefore seek nominations for new members of the Haskell Prime language committee; people who have the enthusiasm to take this forward, as well as some relevant experience. If you think you would like to contribute, please nominate yourself by sending a email to haskell-2011-commit...@haskell.org describing who you are, and what you think the committee might hope to achieve. The address above is populated by the existing committee members, but is now (temporarily) open to all during the nomination period. Nominations close in 3 weeks time, i.e. to be received by end of Sunday 24th February 2013. The process for deciding a new language committee is described at http://hackage.haskell.org/trac/haskell-prime/wiki/Committee Regards, Malcolm ___ Haskell-prime mailing list Haskell-prime@haskell.org http://www.haskell.org/mailman/listinfo/haskell-prime
Re: Bang patterns
On Sun, Feb 3, 2013 at 4:44 PM, Ben Millwood hask...@benmachine.co.uk wrote: I have two proposals, I suppose: - make bang patterns in let altogether invalid I would prefer it to be valid. It's the syntactically most lightweight option we have to force some thunks before using the resulting values in a constructor that we have. Example let !x = ... !y = ... in C x y The alternative would be let x = ... y = ... in x `seq` y `seq` C x y which obscures the code much more. My 2 cents. -- Johan ___ Haskell-prime mailing list Haskell-prime@haskell.org http://www.haskell.org/mailman/listinfo/haskell-prime
RE: Bang patterns
| I have two proposals, I suppose: | - make bang patterns operate only on variables and wildcards | - make bang patterns in let altogether invalid | | Looking at this again made me realise that, as well as !_ and !varid | lexemes, we could also alter the decl production so that we get | decl - ... || pat rhs -- existing lazy binding production || '!' pat rhs -- new strict binding production | | That means that | let !(x, y) = e in ... | would still be valid, with the ! not actually being parsed as part of | the pattern, but would parse instead as a strict binding. Yes, I like this. You could see the '!' pat rhs production as cancelling the implied '~' that a let-binding usually gets (see the desugaring for lets in the report). A bang really only makes sense * At the top of a let, to cancel the implied '~'. Like Johan I am very strongly in favour of using ! for this purpose. * On a varid or '_', which otherwise match lazily Hence Ian's proposal, which treats these two separately, makes sense. For example, there's no point in the pattern (x, !(y,z)), because it behaves identically to (x, (y,z)). We really do need to allow f !x y !z = e to mean f is strict in x and z. There is an ambiguity here with a infix definition of (!), but it must be resolved in favour of the bang-pattern version. I don't have a strong opinion about whether f ! x y ! z = e should mean the same; ie whether the space is significant. I think it's probably more confusing if the space is significant (so its presence or absence makes a difference). Simon ___ Haskell-prime mailing list Haskell-prime@haskell.org http://www.haskell.org/mailman/listinfo/haskell-prime
Re: Bang patterns
On Mon, Feb 04, 2013 at 10:37:44PM +, Simon Peyton-Jones wrote: I don't have a strong opinion about whether f ! x y ! z = e should mean the same; ie whether the space is significant. I think it's probably more confusing if the space is significant (so its presence or absence makes a difference). I also don't feel strongly, although I lean the other way: I don't think anyone writes f ! x when they mean f with a strict argument x, and I don't see any particular advantage in allowing it. In fact, I think writing that is less clear than f !x, so there is an advantage in disallowing it. It also means that existing code that defines a (!) operator in infix style would continue to work, provided it puts whitespace around the !. Thanks Ian ___ Haskell-prime mailing list Haskell-prime@haskell.org http://www.haskell.org/mailman/listinfo/haskell-prime
Re: Bang patterns
On Mon, Feb 04, 2013 at 01:21:31PM -0800, Johan Tibell wrote: On Sun, Feb 3, 2013 at 4:44 PM, Ben Millwood hask...@benmachine.co.uk wrote: I have two proposals, I suppose: - make bang patterns in let altogether invalid I would prefer it to be valid. It's the syntactically most lightweight option we have to force some thunks before using the resulting values in a constructor that we have. Example let !x = ... !y = ... in C x y The alternative would be let x = ... y = ... in x `seq` y `seq` C x y which obscures the code much more. I'd write (C $! x) $! y. We could devise a left-associative $! to avoid the use of parentheses here. But my objection was only ever a mild unease in any case, so I'm happy to dismiss it. Ben ___ Haskell-prime mailing list Haskell-prime@haskell.org http://www.haskell.org/mailman/listinfo/haskell-prime
Re: Bang patterns
If space sensitivity or () disambiguation is being used on !, could one of these also be permitted on ~ to permit it as a valid infix term-level operator? That would be an amazingly valuable symbol to be able to reclaim for the term level for equivalences, and for folks who come from other languages where it is used like liftA2 (,) in parsing libraries, etc. -Edward On Mon, Feb 4, 2013 at 6:42 PM, Ian Lynagh i...@well-typed.com wrote: On Mon, Feb 04, 2013 at 10:37:44PM +, Simon Peyton-Jones wrote: I don't have a strong opinion about whether f ! x y ! z = e should mean the same; ie whether the space is significant. I think it's probably more confusing if the space is significant (so its presence or absence makes a difference). I also don't feel strongly, although I lean the other way: I don't think anyone writes f ! x when they mean f with a strict argument x, and I don't see any particular advantage in allowing it. In fact, I think writing that is less clear than f !x, so there is an advantage in disallowing it. It also means that existing code that defines a (!) operator in infix style would continue to work, provided it puts whitespace around the !. Thanks Ian ___ Haskell-prime mailing list Haskell-prime@haskell.org http://www.haskell.org/mailman/listinfo/haskell-prime ___ Haskell-prime mailing list Haskell-prime@haskell.org http://www.haskell.org/mailman/listinfo/haskell-prime
