[ghc-steering-committee] #216: Qualified Do again, recommendation: accept the alternative

[Simon Peyton Jones]

|  the variant is described in 6.1.2 of the proposal:

PS: Sorry for missing that.  (It has not been mentioned in any of the discussion.)

Simon

|  -----Original Message-----
|  From: ghc-steering-committee <ghc-steering-committee-
|  bounces at haskell.org> On Behalf Of Joachim Breitner
|  Sent: 16 April 2020 15:57
|  To: ghc-steering-committee at haskell.org
|  Subject: Re: [ghc-steering-committee] #216: Qualified Do again,
|  recommendation: accept the alternative
|  
|  Hi,
|  
|  Am Donnerstag, den 16.04.2020, 14:48 +0000 schrieb Simon Peyton Jones
|  via ghc-steering-committee:
|  > It would be really helpful to have a single source of truth.
|  Perhaps
|  > someone (Joachim or anyone else) can write a Google doc that
|  > describes, as precisely as possible, the proposal that he is
|  > advocating.  Or get the proposal authors to do so.   Just saying “a
|  > variant where the value does not need to be in scope” does not count
|  > as a specification (to me).
|  
|  the variant is described in 6.1.2 of the proposal:
|  https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgith
|  ub.com%2Ftweag%2Fghc-proposals%2Fblob%2Flocal-do%2Fproposals%2F0000-
|  local-do.rst%23612qualifieddo-with-operations-that-are-not-in-
|  scope&data=02%7C01%7Csimonpj%40microsoft.com%7Ccfc3548461cb4f9c537
|  b08d7e21665ba%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C63722645813
|  8396283&sdata=fiV%2B37%2BsCuijDL1dx7iyryEkiPWoRC1ZKGtxq4xf9K4%3D&a
|  mp;reserved=0
|  has a spec (“resolves to any (>>=) that is exported by any module
|  aliased by the name M, independently of whether it is in scope (i.e.
|  imported).” and an I think enlightening example (albeit with an odd
|  duplication of imports).
|  
|  > Then.
|  >     1. import MyMonad as M
|  >        (+) other operations do not need to be qualified
|  >        (-) unqualified `>>=` may be ambiguous
|  >
|  > What are “other operations”?
|  
|  Anything else exported from MyMonad that the user might want to use.
|  
|  > Why might “>>=” be ambiguous?  I think the answer is: because
|  MyMonad
|  > must export it (to use in M.do), but it may already be in scope from
|  > the Prelude.
|  
|  Correct.
|  
|  > I’m strongly inclined against inventing new complexity in the module
|  > system, unless it is absolutely unavoidable. More to specify, more
|  to
|  > explain, more to understand, more to implement.
|  
|  And you are sure that the complexity of this is more than that of
|  “fully settled” types?
|  
|  Cheers,
|  Joachim
|  --
|  Joachim Breitner
|    mail at joachim-breitner.de
|  
|  https://nam06.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.j
|  oachim-
|  breitner.de%2F&data=02%7C01%7Csimonpj%40microsoft.com%7Ccfc3548461
|  cb4f9c537b08d7e21665ba%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C63
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