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...@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.schonw...@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.schonw...@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.schonw...@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 <djsamp...@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@haskell.org >>>>> http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs >>>>> >>>> _______________________________________________ >> ghc-devs mailing list >> ghc-devs@haskell.org >> http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs >> >
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