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@haskell.org] On Behalf Of | Richard Eisenberg | Sent: 24 July 2013 12:41 | To: ghc-commits@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 | 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 | | _______________________________________________ | ghc-commits mailing list | ghc-commits@haskell.org | http://www.haskell.org/mailman/listinfo/ghc-commits