[ghc-steering-committee] Proposal: Type Fixity (#65), Recommendation: Reject

Mon Aug 28 12:41:32 UTC 2017

Unsurprisingly, I'm in favor of this proposal and do not wish to reject.

To me, the wart on the language is that we can use the same string for a term-level name and a potentially unrelated type-level name. Of course, this has served many people well, but it does create a certain awkwardness in places (and confusion for beginners!). As long as we have the possibility of one string representing two potentially unrelated names, it seems to be a weakness in expressiveness not to be able to assign different fixities to the names. (And indeed we *can* assign different fixities, as long as we do so in different modules.)

On the other hand, I am sensitive about all those other raw fish that need frying...

Richard

> On Aug 28, 2017, at 5:05 AM, Simon Peyton Jones <simonpj at microsoft.com> wrote:
> 
> I don't have a strong opinion either way. The strongly reason in favour is encapsulated in Richard's comment
> https://github.com/ghc-proposals/ghc-proposals/pull/65#issuecomment-319054892 <https://github.com/ghc-proposals/ghc-proposals/pull/65#issuecomment-319054892>
> which points out that the two T's are entirely unrelated.
>  
> I had not fully realised this, but in fact it is /already/ possible to have different fixities for a single lexeme T; a concrete example is here
> https://github.com/ghc-proposals/ghc-proposals/pull/65#issuecomment-325294776 <https://github.com/ghc-proposals/ghc-proposals/pull/65#issuecomment-325294776>
>  
> I added another comment
> https://github.com/ghc-proposals/ghc-proposals/pull/65#issuecomment-325301080 <https://github.com/ghc-proposals/ghc-proposals/pull/65#issuecomment-325301080>
> that tries to separate the AST issue from the source-code issue.  I do think we should make the internal change; but I’m unconvinced it’s worth the faff to solve the source-level issue.
>  
> Simon
>  
>  
> |  -----Original Message-----
> |  From: ghc-steering-committee [mailto:ghc-steering-committee-
> |  bounces at haskell.org <mailto:bounces at haskell.org>] On Behalf Of Joachim Breitner
> |  Sent: 27 August 2017 19:16
> |  To: ghc-steering-committee at haskell.org <mailto:ghc-steering-committee at haskell.org>
> |  Subject: [ghc-steering-committee] Proposal: Type Fixity (#65),
> |  Recommendation: Reject
> |  
> |  Dear Committee,
> |  
> |  Ryan Scott’s proposal to allow fixity declaration to explicitly target
> |  values or types has been brought before us:
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> |  
> |  I (the secretary) nominates myself as the shepherd, so I can right away
> |  continue giving a recommendation.
> |  
> |  I propose to reject this proposal. The main reasons are:
> |   * it is not clear if there is a real use case for this. Has anyone
> |     ever complained about the status quo?
> |     The proposal does not motivate the need for a change well enough.
> |     (There is a related bug in TH, but that bug can probably simply be
> |     fixed.)
> |   * The status quo can be sold as a feature, rather than a short-coming.
> |     Namely that an operator has a fixed fixity, no matter what namespace
> |     it lives in.
> |     This matches morally what other languages do: In Gallina, fixity
> |     is assigned to names independent of their definition, AFAIK.
> |   * There is a non-trivial implementation and education overhead, a
> |     weight that is not pulled by the gains.
> |  
> |  If we’d design Haskell from scratch, my verdict might possibly be different
> |  (but maybe we wouldn’t even allow types and values to share names then…)
> |  
> |  
> |  Please contradict me or indicate consensus by staying silent.
> |  
> |  
> |  Greetings,
> |  Joachim
> |  
> |  --
> |  Joachim “nomeata” Breitner
> |    mail at joachim-breitner.de <mailto:mail at joachim-breitner.de>
> |  
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