[commit: base] master: Implement "TypeLevelReasoning" proposal at wiki:TypeLevelReasoning (365b9d8)

[Richard Eisenberg]

Re-jig done and committed.

On 2013-07-25 04:06, Simon Peyton-Jones wrote:
> Hs-boot files tend to get in the way of optimisation. Moreover,
> sometimes they are truly necessary, and if there are un-necessary ones
> that can greatly complicate adding necessary ones.   There are already
> LOTS of data types declared as instances of Typeable at the place that
> Typeable class is defined; no harm in one more.
> 
> So I'd really prefer the re-jig if that's ok
> 
> Simon
> 
> |  -----Original Message-----
> |  From: Richard Eisenberg [mailto:eir at cis.upenn.edu]
> |  Sent: 24 July 2013 22:37
> |  To: Simon Peyton-Jones
> |  Cc: ghc-devs at haskell.org
> |  Subject: Re: [commit: base] master: Implement "TypeLevelReasoning" 
> proposal
> |  at wiki:TypeLevelReasoning (365b9d8)
> |
> |  I agree that hs-boot files are a little inelegant, but is there a
> bigger problem with
> |  them? I consider instances to be more tied to a datatype definition
> than the class
> |  definition. It may be possible (I think it is) to avoid the 
> Proxy.hs-boot and
> |  Equality.hs-boot files if we scatter their instances across the
> modules. But, then
> |  the "definition" of these types would be spread across a large
> surface area. To me,
> |  that makes the types harder to update and perhaps harder to
> understand (though
> |  haddock does a nice job of collecting all the instance declarations
> together).
> |
> |  So, my thought is that the mechanism of hs-boot files may be a
> little ugly, but it
> |  makes the code (that is, the collection of instances) easier to
> consider as a whole
> |  and easier to update. That tradeoff seems worthwhile.
> |
> |  That all said, if you (or others) feel strongly about it, I can 
> rejigger it.
> |
> |  Richard
> |
> |  On Jul 24, 2013, at 3:14 PM, Simon Peyton-Jones wrote:
> |
> |  > Richard I am deeply suspicious of all these hs-boot files.
> |  >
> |  > Instances should preferably go EITHER with the data type
> declaration OR with
> |  the class declaration.
> |  >
> |  > In the case of Proxy, for example, why can't the Typeable
> instance for Proxy go
> |  in Data.Typeable.Internals?   (And perhaps similarly for other 
> instances.)
> |  >
> |  > Simon
> |  >
> |  > |  -----Original Message-----
> |  > |  From: ghc-commits [mailto:ghc-commits-bounces at haskell.org] On 
> Behalf Of
> |  > |  Richard Eisenberg
> |  > |  Sent: 24 July 2013 12:41
> |  > |  To: ghc-commits at haskell.org
> |  > |  Subject: [commit: base] master: Implement "TypeLevelReasoning" 
> proposal
> |  at
> |  > |  wiki:TypeLevelReasoning (365b9d8)
> |  > |
> |  > |  Repository : http://darcs.haskell.org/ghc.git/
> |  > |
> |  > |  On branch  : master
> |  > |
> |  > |
> |  
> http://hackage.haskell.org/trac/ghc/changeset/365b9d86d195dc483610a68836b4
> |  > |  063656602244
> |  > |
> |  > |  
> >---------------------------------------------------------------
> |  > |
> |  > |  commit 365b9d86d195dc483610a68836b4063656602244
> |  > |  Author: Richard Eisenberg <eir at cis.upenn.edu>
> |  > |  Date:   Wed Jul 24 12:38:50 2013 +0100
> |  > |
> |  > |      Implement "TypeLevelReasoning" proposal at 
> wiki:TypeLevelReasoning
> |  > |
> |  > |      This commit includes a propositional equality (:=:) in
> Data.Type.Equality,
> |  > |      a Proxy type in Data.Proxy, and has updates to Typeable.
> |  > |
> |  > |      There is an unfortunate number of hs-boot files necessary, 
> but that
> |  > |      seems cleaner than moving Typeable instances around 
> willy-nilly.
> |  > |
> |  > |   Data/Data.hs                   |    2 +-
> |  > |   Data/Proxy.hs                  |  129
> |  > |  ++++++++++++++++++++++++++++++++++++++++
> |  > |   Data/Proxy.hs-boot             |    5 ++
> |  > |   Data/Type/Equality.hs          |   99
> |  > |  ++++++++++++++++++++++++++++++
> |  > |   Data/Type/Equality.hs-boot     |    6 ++
> |  > |   Data/Typeable.hs               |   42 +++++++------
> |  > |   Data/Typeable/Internal.hs      |    5 +-
> |  > |   Data/Typeable/Internal.hs-boot |    3 +-
> |  > |   base.cabal                     |    2 +
> |  > |   9 files changed, 269 insertions(+), 24 deletions(-)
> |  > |
> |  > |
> |  > |  Diff suppressed because of size. To see it, use:
> |  > |
> |  > |      git show 365b9d86d195dc483610a68836b4063656602244
> |  > |
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