Proposal: Partial Type Signatures

[Simon Peyton Jones]

Indeed, you are right.  It's a wiki, so do go ahead.

Simon

| -----Original Message-----
| From: Gabor Greif [mailto:ggreif at gmail.com]
| Sent: 12 March 2014 18:55
| To: Simon Peyton Jones
| Cc: Malcolm Wallace; ghc-devs
| Subject: Re: Proposal: Partial Type Signatures
| 
| Just a reminder that the new jargon is TypedHoles, so maybe the page
| should be renamed to reflect that (an possibly combed for the old
| spelling).
| 
| Cheers,
| 
|     Gabor
| 
| On 3/12/14, Simon Peyton Jones <simonpj at microsoft.com> wrote:
| > http://www.haskell.org/haskellwiki/GHC/TypeHoles
| >
| > | -----Original Message-----
| > | From: ghc-devs [mailto:ghc-devs-bounces at haskell.org] On Behalf Of
| Malcolm
| > | Wallace
| > | Sent: 12 March 2014 18:19
| > | To: ghc-devs
| > | Subject: Re: Proposal: Partial Type Signatures
| > |
| > | Since I never used them, I have honestly been under the impression
| that
| > | the TypeHoles language extension named exactly this partial type
| > | signatures thing.  I have loved the idea of underspecifying the type
| > | signature, ever since it was first mooted many years ago.  So what
| does
| > | TypeHoles do, if not this?
| > |
| > | Regards,
| > |     Malcolm
| > |
| > | On 12 Mar 2014, at 15:09, Edward Kmett wrote:
| > |
| > | > Clearly given that term-level holes are called TypeHoles, the
| extension
| > | to enable these should be called KindHoles. =)
| > | >
| > | > Er.. I'll show myself out.
| > | >
| > | > -Edward
| > | >
| > | >
| > | > On Wed, Mar 12, 2014 at 9:35 AM, Thomas Winant
| > | <thomas.winant at cs.kuleuven.be> wrote:
| > | > 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
| > | >
| > | >
| > | > Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm
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| > | >
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