August 2009 - Haskell-prime

Standarize GHC.Prim.Any
by Maciej Piechotka 06 Sep '09

06 Sep '09

I'm so sorry if I've done it wrong - it's my first contact with Haskell standardization and I base on http://hackage.haskell.org/trac/haskell-prime/wiki/Process . I hope it is not too late as well. Any from GHC.Prim makes unsafeCoerce much useful and safe. Can it be included in Unsafe.Coerce module? Pros: - unsafeCoerce is much more useful with Any (it's a safe placeholder for any value and therefore can be passed simply in/out FFI). Cons: - unsafeCoerce is useful, but not very nice, platorm-dependent low-level anyway. Best regards

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bug in language definition (strictness)
by Malcolm Wallace 01 Sep '09

01 Sep '09

It has been brought to my attention (as errata editor of the revised H'98 report) that there is a bug in the language definition, concerning strictness annotations on datatypes. In section 4.2.1, the translation of strict components of a data constructor is defined as > (\ x1 ... xn -> ( ((K op1 x1) op2 x2) ... ) opn xn) > > where opi is the non-strict apply function $ if si is of the form > ti, and opi is the strict apply function $! (see Section 6.2) if si > is of the form ! ti. Pattern matching on K is not affected by > strictness flags. > yet, because of the definition of $!, this applies the constructor to its arguments right-to-left instead of the intuitive left-to-right. All extant compilers in fact evaluate the strict fields left-to-right in violation of the Report. The same non-intuitive behaviour can be seen more clearly in the simple expression: (f $! x) $! y in which you might expect x to be evaluated before y, but in fact it is the other way round. (And here, the compilers do follow the Report.) The fix I propose for H'98 (and equally for Haskell Prime) is to change the definition of $! as follows Replace f $! x = x `seq` f x with f $! x = f `seq` x `seq` f x in section 6.2 Regards, Malcolm

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Announcing the new Haskell Prime process, and Haskell 2010
by Simon Marlow 20 Aug '09

20 Aug '09

At last year's Haskell Symposium, it was announced that we would change the Haskell Prime process to make it less monolithic. Since then, everyone has been busy using Haskell (or implementing it), and we haven't made much progress on the standardisation side of things. Well, with ICFP and the Haskell Symposium approaching we felt it was time to get the new process moving and hopefully produce a language revision this year. I've updated the Haskell' wiki with the new information; in particular the process is documented here: http://hackage.haskell.org/trac/haskell-prime/wiki/Process We're aiming to announce the list of accepted proposals at the Haskell Symposium this year. However, owing to the short timescale, the list is going to be correspondingly short, and limited to extensions which are either already fully specified (i.e. the FFI) or are small and well-understood. The following list is very provisional; we'll be making the final decisions next month. ForeignFunctionInterface LineCommentSyntax PatternGuards DoAndIfThenElse Remove n+k patterns RelaxedDependencyAnalysis EmptyDataDeclarations HierarchicalModules NonDecreasingIndentation remove FixityResolution from the context-free grammar change the syntax of QualifiedOperators In the coming weeks we'll be refining proposals in preparation for Haskell 2010. By all means suggest more possibilities; however note that as per the new process, a proposal must be "complete" (i.e. in the form of an addendum) in order to be a candidate for acceptance. I have updated the status page http://hackage.haskell.org/trac/haskell-prime/wiki/Status marking everything except the proposals that have been already implemented in the draft Report as "old". The new process requires a proposal to have an owner or owners in order to make progress; once a proposal has an owner it will move into the "under discussion" state. To take up ownership of an existing proposal, or to start a new proposal, ask on the mailing list. There are other ways you can get involved; some suggestions are on the Haskell' main page: http://hackage.haskell.org/trac/haskell-prime/wiki (hmm, I suppose we should fix that logo too...) Cheers, Simon

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StricterLabelledFieldSyntax
by Ian Lynagh 15 Aug '09

15 Aug '09

Hi all, I've made a ticket and proposal page for making the labelled field syntax stricter, e.g. making this illegal: data A = A {x :: Int} y :: Maybe A y = Just A {x = 5} and requiring this instead: data A = A {x :: Int} y :: Maybe A y = Just (A {x = 5}) http://hackage.haskell.org/trac/haskell-prime/ticket/132 http://hackage.haskell.org/trac/haskell-prime/wiki/StricterLabelledFieldSyn… Thanks Ian

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NoMonomorphismRestriction
by Ian Lynagh 07 Aug '09

07 Aug '09

Hi all, I've made a ticket and proposal page for removing the monomorphism restriction: http://hackage.haskell.org/trac/haskell-prime/ticket/131 http://hackage.haskell.org/trac/haskell-prime/wiki/NoMonomorphismRestriction Thanks Ian

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