In all honesty, Typing Haskell in Haskell is about as far as anyone
should push typechecking and type inference while claiming to still work
in a functional style. I don't think a good GADT pre-spec looks like
functional programming at all, it's a [constraint] logic programming
problem and part of what we're looking to establish is the minimum
information flow people can expect during inference for a given amount
of syntactic effort.
I'm not saying I never write the implementations in haskell! But they
tend to involve a lot of "how to implement the constraint system" and
then a bunch of transliterated typing rules. A good spec for "enough
annotation this should work easily" would be useful as something that
permits other implementations to experiment with different extensions in
combination though!
On 22/04/2016 18:55, José Manuel Calderón Trilla wrote:
Hi Richard,
As a concrete suggestion, I wonder if we should have two goals:
1. Write down an updated standard for Haskell.
2. Write down pre-standards for several extensions.
I agree with both of these. It may even be useful to use goal 2 as a
stepping stone to determine what extensions should receive the extra
attention necessary (if any) to be part of goal 1. Were you thinking
that these pre-standards would look something like Mark Jones's
'Typing Haskell in Haskell' paper? A simplified and clear
specification in the form of a Haskell program would go a long way in
clarifying the meaning of certain extensions. To use your example, you
could imagine an implementation of GADTs that forms the baseline of
what the GADT extension should mean (implementations should accept at
least what this one does). That might be too ambitious though.
A lot of the 'obvious' extensions were discussed that last time the
Haskell Prime committee was active, so a lot of groundwork has been
laid already. The most important step right now is empowering people
to move forward with the process.
Herbert Valerio Riedel is the chair of the reboot, and as such gets
final say on who is a member of the committee and any timeline for
deciding. That being said, I think the aim should be to have the
committee membership decided soon and start discussing what the
priorities should be. I'm partial to suggesting a face to face meeting
at ICFP, but realize that it is difficult for many to attend to ICFP.
Cheers,
José
On Fri, Apr 22, 2016 at 9:33 AM, Richard Eisenberg <e...@cis.upenn.edu> wrote:
I stand by ready to debate standards and would enjoy moving this process
forward. However, I'm not in a position where I can lead at the moment -- just
too consumed by other tasks right now.
As a concrete suggestion, I wonder if we should have two goals:
1. Write down an updated standard for Haskell.
2. Write down pre-standards for several extensions.
About (2): I'm very sympathetic to a recent post on Haskell-cafe about having formal
descriptions of language extensions. It is not our purview to document GHC. However,
several extensions are in very common use, but might not be quite ready for a language
standard. Chief among these, in my opinion, is GADTs. GADTs are problematic from a
standardization standpoint because it's quite hard to specify when a GADT pattern-match
type-checks, without resorting to discussion of unification variables. For this reason, I
would be hesitant about putting GADTs in a standard. On the other hand, it shouldn't be
too hard to specify some sort of minimum implementation that individual compilers can
build on. I'm calling such a description a "pre-standard".
Thoughts?
Richard
On Apr 21, 2016, at 5:22 PM, José Manuel Calderón Trilla <j...@jmct.cc> wrote:
Hello all,
I'm curious if there is any progress on the reboot of the Haskell
Prime committee. It has been six months since the closing of
nominations and there hasn't been any word that I'm aware of. I've
also spoken to a few others that have self-nominated and they too have
not heard any news.
Personally, I feel that a new standard is very important for the
future health of the community. Several threads on the mailing list
and posts on the web, such as one on reddit today [1], show a desire
from the community for a major consolidation effort.
If there is any way that I can help the process along I would be glad
to do so. It would be a shame to allow for the enthusiasm for a new
committee fade away.
Cheers,
José
[1]:
https://www.reddit.com/r/haskell/comments/4fsuvu/can_we_have_xhaskell2016_which_turns_on_the_most/
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