Type family equation violates injectivity?

Fri Jan 4 15:04:17 UTC 2019

Would it be easier if you can do a conjunction on vector and base version
in your cpp should you want to support both sides ?

On Fri, Jan 4, 2019 at 9:59 AM Alexander V Vershilov <
alexander.vershilov at gmail.com> wrote:

> For inline-r we have added a revision that sets upper limit, so now
> hackage and stackage should both be happy. I'm not sure if any Linux
> distribution provides inline-r as a package but that should be normal
> situation for them. Next version will either set lower dependency boundary
> or will keep a code that will run with both APIs. So from my perspective
> any solution (even keeping things as-is) will be ok.
>
>
> On Fri, Jan 4, 2019, 17:31 Carter Schonwald <carter.schonwald at gmail.com
> wrote:
>
>> Hrmmm.  Here’s what I’ll do: I’ll make the same release a minor version
>> bump and make the bug fix bump version unbuildable.
>>
>> Would this help matters ?
>>
>> On Fri, Jan 4, 2019 at 9:23 AM Carter Schonwald <
>> carter.schonwald at gmail.com> wrote:
>>
>>> Yeah, I later found it impacted one of my own pieces of code too, in
>>> that I needed to make still further type families injective.
>>>
>>> I do think that a lot of vectors current module structure reflects a
>>> desire for injectivity coupled with historical a lack of mechanism for
>>> guaranteeing it.
>>>
>>> Mess up on my part for sure.  :)
>>>
>>> On Fri, Jan 4, 2019 at 8:11 AM Boespflug, Mathieu <m at tweag.io> wrote:
>>>
>>>> Hi Carter,
>>>>
>>>> thanks for looking into this. We were initially surprised to see a
>>>> breaking change in a point release, but no biggy. It's pretty hard to offer
>>>> strong stability guarantees without automated tooling to catch this kind of
>>>> thing, and these things happen. We'll patch up HaskellR shortly.
>>>>
>>>> Best,
>>>>
>>>>
>>>> On Sun, 30 Dec 2018 at 01:06, Carter Schonwald <
>>>> carter.schonwald at gmail.com> wrote:
>>>>
>>>>> To be clear : I’m annoyed with myself that this impacted a package
>>>>> that depends on vector, but this does seem to be the case that the newest
>>>>> bug fix release for vector actually revealed a broken design for the vector
>>>>> instances / data types in the inline-r package.
>>>>>
>>>>> To;dr — I suggest patching inline-r to remove the s parameter in its
>>>>> immutable vector data types
>>>>>
>>>>> On Sat, Dec 29, 2018 at 6:48 PM Carter Schonwald <
>>>>> carter.schonwald at gmail.com> wrote:
>>>>>
>>>>>> so i took a look .. (also the inline-r devs seem to have done a
>>>>>> hackage revision so you wont hit that issue in your current setup if you do
>>>>>> a cabal update ..)
>>>>>> and it seems like the type definitions in inline-r are kinda bogus
>>>>>> and you should get them patched ...
>>>>>>
>>>>>> the MVector type class, and related type families, all assume your
>>>>>> mutable type has the last two arguments as the io/state token and then the
>>>>>> element type
>>>>>>
>>>>>> eg
>>>>>> basicLength :: v s a -> Int
>>>>>> <http://hackage.haskell.org/package/base-4.12.0.0/docs/Data-Int.html#t:Int>
>>>>>>
>>>>>>
>>>>>> i looked at
>>>>>> https://github.com/tweag/HaskellR/blob/1292c8a9562764d34ee4504b54d93248eb7346fe/inline-r/src/Data/Vector/SEXP.hs#L346-L374
>>>>>> and
>>>>>>
>>>>>>
>>>>>>
>>>>>> as a point of grounding this chat
>>>>>> the injective type familly in question is defined by the follwoing
>>>>>>
>>>>>>
>>>>>> --#if MIN_VERSION_base(4,9,0)type family Mutable <http://hackage.haskell.org/package/vector-0.12.0.2/docs/src/Data.Vector.Generic.Base.html#Mutable> (v <http://hackage.haskell.org/package/vector-0.12.0.2/docs/src/Data.Vector.Generic.Base.html#local-6989586621679032525> :: * -> *) = (mv <http://hackage.haskell.org/package/vector-0.12.0.2/docs/src/Data.Vector.Generic.Base.html#local-6989586621679032526> :: * -> * -> *) | mv -> v#elsetype family Mutable (v :: * -> *) :: * -> * -> *#endif
>>>>>>
>>>>>> anyways, it looks like the Pure / immutable vector data type in
>>>>>> inline-r has a spurious state token argument in its definition that
>>>>>> shouldn't be there, OR there need to be two "s" params in inline-r instead
>>>>>> of the one
>>>>>>
>>>>>> heres the full code i linked to in question
>>>>>>
>>>>>>
>>>>>> -- | Mutable R vector. Represented in memory with the same header as
>>>>>> 'SEXP'
>>>>>>
>>>>>> -- nodes. The second type parameter is phantom, reflecting at the
>>>>>> type level the
>>>>>> -- tag of the vector when viewed as a 'SEXP'. The tag of the vector
>>>>>> and the
>>>>>> -- representation type are related via 'ElemRep'.
>>>>>> data MVector s ty a = MVector
>>>>>> { mvectorBase :: {-# UNPACK #-} !(SEXP s ty)
>>>>>> , mvectorOffset :: {-# UNPACK #-} !Int32
>>>>>> , mvectorLength :: {-# UNPACK #-} !Int32
>>>>>> }
>>>>>> -- | Internal wrapper type for reflection. First type parameter is
>>>>>> the reified
>>>>>> -- type to reflect.
>>>>>> newtype W t ty s a = W { unW :: MVector s ty a }
>>>>>> instance (Reifies t (AcquireIO s), VECTOR s ty a) => G.MVector (W t
>>>>>> ty) a where
>>>>>>
>>>>>> data Vector s (ty :: SEXPTYPE) a = Vector
>>>>>>     { vectorBase :: {-# UNPACK #-} !(ForeignSEXP ty) , vectorOffset
>>>>>> :: {-# UNPACK #-} !Int32 , vectorLength :: {-# UNPACK #-} !Int32
>>>>>> }
>>>>>>
>>>>>>
>>>>>> type instance G.Mutable (W t ty s) = Mutable.W t ty
>>>>>> Anyways, the fix here is to remove the s param from the Pure version
>>>>>> of W and "Sexp Vector"
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Sat, Dec 29, 2018 at 6:16 PM Carter Schonwald <
>>>>>> carter.schonwald at gmail.com> wrote:
>>>>>>
>>>>>>> were you using the same version of vector in both setups?
>>>>>>>
>>>>>>> in the most recent  vector release  we made mutable type family
>>>>>>> injective in the vector package for ghc's that support it ...
>>>>>>>
>>>>>>> On Sat, Dec 29, 2018 at 1:50 PM Dominick Samperi <
>>>>>>> djsamperi at gmail.com> wrote:
>>>>>>>
>>>>>>>> When I use v8.6.3 of GHC under Ubuntu to install the inline-r
>>>>>>>> package
>>>>>>>> I get the error "Type family equation violates injectivity
>>>>>>>> annotation," and
>>>>>>>> a type variable on the LHS cannot be inferred from the RHS, due to
>>>>>>>> the lack of injectivity (I suppose).
>>>>>>>>
>>>>>>>> On the other hand, v8.0.2 of GHC (shipped with Haskell Platform
>>>>>>>> under
>>>>>>>> Ubuntu) does not have this problem (it has other problems).
>>>>>>>>
>>>>>>>> Has something changed in the latest version of the compiler that
>>>>>>>> might
>>>>>>>> cause this? Possible work-around?
>>>>>>>>
>>>>>>>> FYI, the line that triggers the error is:
>>>>>>>> type instance G.Mutable (W t ty s) = Mutable.W t ty
>>>>>>>>
>>>>>>>> The variable that cannot be inferred is 's'.
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>> Dominick
>>>>>>>> _______________________________________________
>>>>>>>> ghc-devs mailing list
>>>>>>>> ghc-devs at haskell.org
>>>>>>>> http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs
>>>>>>>>
>>>>>>> _______________________________________________
>>>>> ghc-devs mailing list
>>>>> ghc-devs at haskell.org
>>>>> http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs
>>>>>
>>>> _______________________________________________
>> ghc-devs mailing list
>> ghc-devs at haskell.org
>> http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.haskell.org/pipermail/ghc-devs/attachments/20190104/19fe223d/attachment.html>