GHC 7.10 Prelude: we need your opinion

[Miguel]

What were the objections? Especially the principle ones?

On Tue, Feb 10, 2015 at 4:50 PM, Simon Peyton Jones <simonpj at microsoft.com>
wrote:

>  Haskell Friends
>
> *This email asks for your help in deciding how to proceed with some
> Prelude changes in GHC 7.10.  Please read on, but all the info is also at
> the survey link, here: http://goo.gl/forms/XP1W2JdfpX
> <http://goo.gl/forms/XP1W2JdfpX>.   Deadline is 21 Feb.*
>
>
>
> The ​Core Libraries Committee (CLC) is responsible for developing the core
> libraries that ship with GHC. This is an important but painstaking task,
> and we owe the CLC a big vote of thanks for taking it on.
>
> For over a year the CLC has been working on integrating the *Foldable and
> Traversable classes* (shipped in base in GHC 7.8) into the core
> libraries, and into the Prelude in particular. Detailed planning for GHC
> 7.10 started in the autumn of 2014, and the CLC went ahead with this
> integration.
>
> Then we had a failure of communication.  As these changes affect the
> Prelude, which is in scope for all users of Haskell, these changes should
> be held to a higher bar than the regular libraries@ review process.
> However, the Foldable/Traversable changes were not particularly well
> signposted. Many people have only recently woken up to them, and some have
> objected (both in principle and detail).
>
> This is an extremely unfortunate situation. On the one hand we are at RC2
> for GHC 7.10, so library authors have invested effort in updating their
> libraries to the new Prelude. On the other, altering the Prelude is in
> effect altering the language, something we take pretty seriously. We should
> have had this debate back in 2014, but here we are, and it is unproductive
> to argue about whose fault it is. We all share responsibility.
>
> We need to decide what to do now. A small group of us met by Skype and
> we've decided to do this:
>
> ·         Push back GHC 7.10's release by at least a month, to late
> March.  This delay also gives us breathing space to address an unrelated
> show-stopping bug, Trac #9858.
>
> ·         Invite input from the Haskell community on which of two
> approaches to adopt (this survey <http://goo.gl/forms/XP1W2JdfpX>).  The
> main questions revolve around impact on the Haskell ecosystem (commercial
> applications, teaching, libraries, etc etc), so we want to ask your opinion
> rather than guess it.
>
> ·         Ask Simon Marlow and Simon Peyton Jones to decide which
> approach to follow for GHC 7.10.
>
> Wiki pages have been created summarizing these two primary alternatives,
> including many more points and counter-points and technical details:
>
> ·         Overall summary:
> https://ghc.haskell.org/trac/ghc/wiki/Prelude710
> <https://www.google.com/url?q=https%3A%2F%2Fghc.haskell.org%2Ftrac%2Fghc%2Fwiki%2FPrelude710&sa=D&sntz=1&usg=AFQjCNE1p5w-YCXC7ixebvwObayuV7Ut4w>
>
> ·         Details of Plan List:
> https://ghc.haskell.org/trac/ghc/wiki/Prelude710/List
> <https://www.google.com/url?q=https%3A%2F%2Fghc.haskell.org%2Ftrac%2Fghc%2Fwiki%2FPrelude710%2FList&sa=D&sntz=1&usg=AFQjCNHaufeSwtIsvZwdVXwP9F9G45zLSA>
>
> ·         Details of Plan FTP:
> https://ghc.haskell.org/trac/ghc/wiki/Prelude710/FTP
> <https://www.google.com/url?q=https%3A%2F%2Fghc.haskell.org%2Ftrac%2Fghc%2Fwiki%2FPrelude710%2FFTP&sa=D&sntz=1&usg=AFQjCNHbhNyIwAbcOd3JfikIhD6S7rc-vw>
>
> This survey invites your input on which plan we should follow. Would you
> please
>
> ·         Read the details of the alternative plans on the three wiki
> pages above
>
> ·         Add your response to the survey <http://goo.gl/forms/XP1W2JdfpX>
>
> Please do read the background.  Well-informed responses will help.  Thank
> you!
>
> *DEADLINE: 21 February 2015*
>
> Simon PJ
>
> _______________________________________________
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>
>
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