Ahn, Ki Yung wrote:
Another problem, which I haven't mentioned, I have when I tried to make
additional type family instance declarations that latest (stable)
Typo: I mean type class instance declaration of course.
distributions of GHC 6.10.x does not let me declare instances of
(Expandable (Tuple (Map ((,) t2) ys))). When you try declaring such an
instance something like this:
> instance Expandable (Tuple (Map ((,) t2) ys)) where
> ...
GHC will give me an error message that type synonyms are not allowed in
instance declarations:
kya...@kyavaio:~/tmp$ ghci -fglasgow-exts -XUndecidableInstances
Review3.lhs
GHCi, version 6.10.3: http://www.haskell.org/ghc/ :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer ... linking ... done.
Loading package base ... linking ... done.
[1 of 1] Compiling Main ( Review3.lhs, interpreted )
Review3.lhs:62:2:
Illegal type synonym family application in instance:
Tuple (Map ((,) t2) ys)
In the instance declaration for `Expandable (Tuple (Map ((,) t2) ys))'
Failed, modules loaded: none.
So, my impression is that there is little hope even I try fixing this by
adding more instance declarations, even if this was an incomplete code
because of space restrictions of the review. But I still wanted to
double check and discuss this matter with mailing list readers since
there were few reports (which we fail to reproduce) that this type
checks in their installation of GHC.
_______________________________________________
Glasgow-haskell-users mailing list
Glasgow-haskell-users@haskell.org
http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
