Proposal: Partial Type Signatures

[Simon Peyton Jones]

| Excellent, I added responses ("thomasw") to your comments on the wiki
| page.

OK, good. Better still, improve your wording so that no one could make the same mistake as I did, and delete both comments.

Simon

| -----Original Message-----
| From: Thomas Winant [mailto:thomas.winant at cs.kuleuven.be]
| Sent: 13 March 2014 19:38
| To: Simon Peyton Jones; ghc-devs at haskell.org
| Cc: Tom Schrijvers; Frank Piessens
| Subject: Re: Proposal: Partial Type Signatures
| 
| On 13-03-14 10:46, Simon Peyton Jones wrote:
| > | Together with Tom Schrijvers, Frank Piessens and Dominique Devriese,
| > | I have been working on a proposal for adding *Partial Type
| > | Signatures* to GHC.
| >
| > I'm all for this.  Yes, if the design and implementation are solid,
| I'd be happy to add it to the main branch.
| >
| > Do focus on something with excellent power-to-weight ratio: that is,
| gives a lot of benefit for a small cost, rather than something that
| gives 10% more benefit for 200% more cost.
| >
| > I've annotated the wiki page with some "SLPJ" comments, which you may
| want to look at.
| >
| > I'd be happy to have a Skype conversation about the details in due
| course.
| 
| Excellent, I added responses ("thomasw") to your comments on the wiki
| page.
| 
| Cheers,
| Thomas
| 
| 
| > | -----Original Message-----
| > | From: ghc-devs [mailto:ghc-devs-bounces at haskell.org] On Behalf Of
| > | Thomas Winant
| > | Sent: 12 March 2014 13:36
| > | To: ghc-devs at haskell.org
| > | Cc: Tom Schrijvers; Frank Piessens
| > | Subject: Proposal: Partial Type Signatures
| > |
| > | Dear GHC developers,
| > |
| > | Together with Tom Schrijvers, Frank Piessens and Dominique Devriese,
| > | I have been working on a proposal for adding *Partial Type
| > | Signatures* to GHC. In a partial type signature, annotated types can
| > | be mixed with inferred types. A type signature is written like
| > | before, but can now contain wildcards, written as underscores. The
| > | types of these wildcards or unknown types will be inferred by the
| type checker, e.g.
| > |
| > |      foo :: _ -> Bool
| > |      foo x = not x
| > |      -- Inferred: Bool -> Boo
| > |
| > | The proposal also includes a form of generalisation which aligns
| > | with the existing generalisation that GHC does. We have written down
| > | a motivation (when and how might you use this) and details about the
| > | design and implementation on the following wiki page:
| > |
| > | https://ghc.haskell.org/trac/ghc/wiki/PartialTypeSignatures
| > |
| > | We have a (work in progress) implementation [1] of the feature based
| > | on GHC. It currently implements most of what we propose, but there
| > | are some remaining important bugs mostly concerning the
| > | generalisation. We also described our design and presented a
| > | formalisation based on the
| > | OutsideIn(X) formalism in a paper [2] presented at PADL'14.
| > |
| > | What we are hoping to get from the people on this list is any of the
| > | below:
| > | * Read the design, play with the implementation and tell us any
| comments
| > |    you may have about the feature, its design and implementation.
| > | * Opinions on whether this feature might be acceptable in GHC
| upstream
| > |    at some point (if not, we do not think it's worth developing the
| > |    implementation much further).
| > | * Perhaps a code review or a discussion with someone more
| knowledgeable
| > |    about the internals of GHC's type checker about how we might fix
| the
| > |    remaining problems in our implementation (specifically, we could
| use
| > |    some help with implementing the generalisation of partial type
| > |    signatures).
| > | * Feedback on the `Questions and issues' section on the wiki page.
| > |
| > |
| > | Kind regards,
| > | Thomas Winant
| > |
| > | [1]: https://github.com/mrBliss/ghc-head/
| > | [2]:
| > | https://lirias.kuleuven.be/bitstream/123456789/423475/3/paper.pdf
| > |
| > |
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| >
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