Re: [Haskell-cafe] A pattern type signature cannot bind scoped type variables `t'
On Mon, 2009-01-12 at 20:24 -0200, rodrigo.bonifacio wrote: > Hi all, > > I'm trying to build a library that has the following code: > > hasTypeOf (TermRep (dx,_,_)) (x::t) > = ((fromDynamic dx)::Maybe t) > Could you do something like this? Enforce the types with a signature: hasTypeOf :: (Typeable t) => Dynamic -> t -> Maybe t hasTypeOf x _ = fromDynamic x > hasTypeOf (toDyn (2::Int)) (undefined::Integer) Nothing > hasTypeOf (toDyn (2::Int)) (undefined::Int) Just 2 Or if you just want boolean result: hasTypeOf x y = typeOf y == dynTypeRep x rcmAttmntN3MDzg Description: micalg/pgp-sha1 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] A pattern type signature cannot bind scoped type variables `t'
Hi all, I'm trying to build a library that has the following code: hasTypeOf (TermRep (dx,_,_)) (x::t) = ((fromDynamic dx)::Maybe t) When I try to compile with ghc-6.8.3 I got the following error: ../../StrategyLib/models/drift-default//TermRep.hs:63:30: A pattern type signature cannot bind scoped type variables `t' unless the pattern has a rigid type context In the pattern: x :: t In the definition of `hasTypeOf': hasTypeOf (TermRep (dx, _, _)) (x :: t) = ((fromDynamic dx) :: Maybe t) How can I solve this problem? Is there any option to ignore this erro when compiling with ghc-6.8.3? Thanks for any help. Rodrigo. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
