Hello,
The discussion on the libraries list is archived here:
http://www.haskell.org/pipermail/libraries/2011-September/016699.html
There hasn't been a corresponding discussion for Haskell Prime so,
technically, GHC deviates from the standard.
-Iavor
On Fri, Dec 23, 2011 at 9:41 AM, Simon Peyton-Jones
simo...@microsoft.com wrote:
I'm confused too. I'd welcome clarification from the Haskell Prime folk.
S
-Original Message-
From: Serge D. Mechveliani [mailto:mech...@botik.ru]
Sent: 23 December 2011 17:36
To: Simon Peyton-Jones
Subject: Re: 7.4.1-pre: Show Integral
On Thu, Dec 22, 2011 at 08:14:54PM +, Simon Peyton-Jones wrote:
| 2011/12/22 Edward Kmett ekm...@gmail.com:
| The change, however, was a deliberate _break_ with the standard that
| passed through the library review process a few months ago, and is now
| making its way out into the wild.
|
| Is it reasonable to enquire how many standard-compliant implementations
| of Haskell there are?
Just to be clear, the change IS the standard. GHC has to change to be
compliant.
At least that's how I understand it.
I am confused.
I am looking now at the on-line specification of Haskell-2010,
6.3 Standard Haskell Classes.
It shows that Integral includes Show:
Eq Show
\ /
Num
|
Enum Real
\ |
Integral
This is also visible in the further standard class declarations in this
chapter.
Hence, for `x :: Integral a = a' it is correct to write (shows x ).
And ghc-7.4.0.20111219 does not allow this.
So, ghc-7.4.0.20111219 breaks the 2010 standard. Now, Edward Kmett writes
that
this break is done deliberately.
Am I missing something?
I witness this for the first time: that GHC deliberately breaks the current
Haskell standard.
Probably, many people (as myself) dislike this point of the standard.
Well, they can write a dummy Show implementation for their type T:
showsPrec _ _ = showString (t :: T),
and wait for an improved standard, say, Haskell-II
-- ?
Regards,
--
Sergei
mech...@botik.ru
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