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Known problems with promoted tuples and lists in GHC 7.4.1?

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David Menendez-2

Known problems with promoted tuples and lists in GHC 7.4.1?

Are there any known issues involving type-level pairs and lists? I've
hit a few baffling type errors that went away when I refactored my
code to use locally-defined pairs and lists instead of those provided
by the prelude.

More worryingly, I had one function that would stop passing the type
checker if I replaced '[n] with (n ': '[]) in its signature.

--
Dave Menendez <[hidden email]>
<http://www.eyrie.org/~zednenem/>

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José Pedro Magalhães

Re: Known problems with promoted tuples and lists in GHC 7.4.1?

Hi David,

Are you using HEAD? If so, and you run into problems, please report them (either here or as bugs in trac).

Thanks,
Pedro

On Wed, Jun 6, 2012 at 9:37 PM, David Menendez <[hidden email]> wrote:

Are there any known issues involving type-level pairs and lists? I've
hit a few baffling type errors that went away when I refactored my
code to use locally-defined pairs and lists instead of those provided
by the prelude.

More worryingly, I had one function that would stop passing the type
checker if I replaced '[n] with (n ': '[]) in its signature.

--
Dave Menendez <[hidden email]>
<http://www.eyrie.org/~zednenem/>

_______________________________________________
Glasgow-haskell-users mailing list
[hidden email]
http://www.haskell.org/mailman/listinfo/glasgow-haskell-users

_______________________________________________
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[hidden email]
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David Menendez-2

Re: Known problems with promoted tuples and lists in GHC 7.4.1?

No, I'm just running 7.4.1.

Here's a very stripped-down example of what I'm seeing:

{-# LANGUAGE PolyKinds, DataKinds #-}

data Pair a b = P a b
data Nat = Z | S Nat

data Phantom i = Phantom

okay :: Phantom ('P Int Int)
okay = Phantom

-- not_okay :: Phantom '(Int, Int)
-- not_okay = Phantom

Uncommenting that last bit results in this error,

Couldn't match kind `BOX' against `*'
Kind incompatibility when matching types:
k0 :: BOX
(*, *) :: *
In the expression: Phantom
In an equation for `not_okay': not_okay = Phantom

Something seems to have gone wrong internally.

On Wed, Jun 6, 2012 at 5:43 PM, José Pedro Magalhães <[hidden email]> wrote:

> Hi David,
>
> Are you using HEAD? If so, and you run into problems, please report them
> (either here or as bugs in trac).
>
>
> Thanks,
> Pedro
>
> On Wed, Jun 6, 2012 at 9:37 PM, David Menendez <[hidden email]> wrote:
>>
>> Are there any known issues involving type-level pairs and lists? I've
>> hit a few baffling type errors that went away when I refactored my
>> code to use locally-defined pairs and lists instead of those provided
>> by the prelude.
>>
>> More worryingly, I had one function that would stop passing the type
>> checker if I replaced '[n] with (n ': '[]) in its signature.
>>
>> --
>> Dave Menendez <[hidden email]>
>> <http://www.eyrie.org/~zednenem/>
>>
>> _______________________________________________
>> Glasgow-haskell-users mailing list
>> [hidden email]
>> http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
>
>

--
Dave Menendez <[hidden email]>
<http://www.eyrie.org/~zednenem/>

_______________________________________________
Glasgow-haskell-users mailing list
[hidden email]
http://www.haskell.org/mailman/listinfo/glasgow-haskell-users

Simon Peyton-Jones

RE: Known problems with promoted tuples and lists in GHC 7.4.1?

Kind polymorphism and promoted kinds is *not* an advertised feature of 7.4.1. Much code is there, but it doesn't work when you push it. The HEAD does work. If you are using kind polymorphism or promoted kinds, use HEAD (or a development snapshot).

Indeed not_okay compiles fine with HEAD

Simon

| -----Original Message-----
| From: [hidden email] [mailto:glasgow-haskell-
| [hidden email]] On Behalf Of David Menendez
| Sent: 06 June 2012 23:50
| To: José Pedro Magalhães
| Cc: [hidden email] Mailing List
| Subject: Re: Known problems with promoted tuples and lists in GHC 7.4.1?
|
| No, I'm just running 7.4.1.
|
| Here's a very stripped-down example of what I'm seeing:
|
| {-# LANGUAGE PolyKinds, DataKinds #-}
|
| data Pair a b = P a b
| data Nat = Z | S Nat
|
| data Phantom i = Phantom
|
| okay :: Phantom ('P Int Int)
| okay = Phantom
|
| -- not_okay :: Phantom '(Int, Int)
| -- not_okay = Phantom
|
| Uncommenting that last bit results in this error,
|
| Couldn't match kind `BOX' against `*'
| Kind incompatibility when matching types:
| k0 :: BOX
| (*, *) :: *
| In the expression: Phantom
| In an equation for `not_okay': not_okay = Phantom
|
| Something seems to have gone wrong internally.
|
|
| On Wed, Jun 6, 2012 at 5:43 PM, José Pedro Magalhães <[hidden email]>
| wrote:
| > Hi David,
| >
| > Are you using HEAD? If so, and you run into problems, please report
| > them (either here or as bugs in trac).
| >
| >
| > Thanks,
| > Pedro
| >
| > On Wed, Jun 6, 2012 at 9:37 PM, David Menendez <[hidden email]>
| wrote:
| >>
| >> Are there any known issues involving type-level pairs and lists? I've
| >> hit a few baffling type errors that went away when I refactored my
| >> code to use locally-defined pairs and lists instead of those provided
| >> by the prelude.
| >>
| >> More worryingly, I had one function that would stop passing the type
| >> checker if I replaced '[n] with (n ': '[]) in its signature.
| >>
| >> --
| >> Dave Menendez <[hidden email]>
| >> <http://www.eyrie.org/~zednenem/>
| >>
| >> _______________________________________________
| >> Glasgow-haskell-users mailing list
| >> [hidden email]
| >> http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
| >
| >
|
|
|
| --
| Dave Menendez <[hidden email]>
| <http://www.eyrie.org/~zednenem/>
|
| _______________________________________________
| Glasgow-haskell-users mailing list
| [hidden email]
| http://www.haskell.org/mailman/listinfo/glasgow-haskell-users

_______________________________________________
Glasgow-haskell-users mailing list
[hidden email]
http://www.haskell.org/mailman/listinfo/glasgow-haskell-users

David Menendez-2

Re: Known problems with promoted tuples and lists in GHC 7.4.1?

On Thu, Jun 7, 2012 at 2:37 AM, Simon Peyton-Jones
<[hidden email]> wrote:
> Kind polymorphism and promoted kinds is *not* an advertised feature of 7.4.1. Much code is there, but it doesn't work when you push it. The HEAD does work. If you are using kind polymorphism or promoted kinds, use HEAD (or a development snapshot).

I'll keep that in mind if I do anything serious. For now, I've been
able to work around the oddity by using my own pairs and lists. If
anything, it works better than I expected.

> Indeed not_okay compiles fine with HEAD

Glad to hear it.

> | -----Original Message-----
> | From: [hidden email] [mailto:glasgow-haskell-
> | [hidden email]] On Behalf Of David Menendez
> | Sent: 06 June 2012 23:50
> | To: José Pedro Magalhães
> | Cc: [hidden email] Mailing List
> | Subject: Re: Known problems with promoted tuples and lists in GHC 7.4.1?
> |
> | No, I'm just running 7.4.1.
> |
> | Here's a very stripped-down example of what I'm seeing:
> |
> | {-# LANGUAGE PolyKinds, DataKinds #-}
> |
> | data Pair a b = P a b
> | data Nat = Z | S Nat
> |
> | data Phantom i = Phantom
> |
> | okay :: Phantom ('P Int Int)
> | okay = Phantom
> |
> | -- not_okay :: Phantom '(Int, Int)
> | -- not_okay = Phantom
> |
> | Uncommenting that last bit results in this error,
> |
> | Couldn't match kind `BOX' against `*'
> | Kind incompatibility when matching types:
> | k0 :: BOX
> | (*, *) :: *
> | In the expression: Phantom
> | In an equation for `not_okay': not_okay = Phantom
> |
> | Something seems to have gone wrong internally.
> |
> |
> | On Wed, Jun 6, 2012 at 5:43 PM, José Pedro Magalhães <[hidden email]>
> | wrote:
> | > Hi David,
> | >
> | > Are you using HEAD? If so, and you run into problems, please report
> | > them (either here or as bugs in trac).
> | >
> | >
> | > Thanks,
> | > Pedro
> | >
> | > On Wed, Jun 6, 2012 at 9:37 PM, David Menendez <[hidden email]>
> | wrote:
> | >>
> | >> Are there any known issues involving type-level pairs and lists? I've
> | >> hit a few baffling type errors that went away when I refactored my
> | >> code to use locally-defined pairs and lists instead of those provided
> | >> by the prelude.
> | >>
> | >> More worryingly, I had one function that would stop passing the type
> | >> checker if I replaced '[n] with (n ': '[]) in its signature.
> | >>
> | >> --
> | >> Dave Menendez <[hidden email]>
> | >> <http://www.eyrie.org/~zednenem/>
> | >>
> | >> _______________________________________________
> | >> Glasgow-haskell-users mailing list
> | >> [hidden email]
> | >> http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
> | >
> | >
> |
> |
> |
> | --
> | Dave Menendez <[hidden email]>
> | <http://www.eyrie.org/~zednenem/>
> |
> | _______________________________________________
> | Glasgow-haskell-users mailing list
> | [hidden email]
> | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
>
>