hi,
i'm trying to get labelled records working with the current version of HList.
i've got code that looks like:
>{-# language EmptyDataDecls #-}
>module Tst where
> import Data.HList
>
> data Foo; foo = proxy::Proxy Foo
> data Bar; bar = proxy::Proxy Bar
> rec1 =
> foo .=. 1 .*.
> bar .=. "hello" .*.
> emptyRecord
which gives me the error:
Tst4.hs:8:2:
No instance for (HEq (Proxy Foo) (Proxy Bar) HFalse)
arising from a use of `.*.' at Tst4.hs:(8,2)-(10,12)
Possible fix:
add an instance declaration for
(HEq (Proxy Foo) (Proxy Bar) HFalse)
In the expression: foo .=. 1 .*. bar .=. "hello" .*. emptyRecord
In the definition of `rec1':
rec1 = foo .=. 1 .*. bar .=. "hello" .*. emptyRecord
some discussion on #haskell suggesting importing Label4 and TypeEqGeneric1
but a) that's not possible because both are hidden inside the HList package
and b) even when i get around that restriction, i still get a "No instance
for (TypeCast HFalse HFalse)" error.
thanks,
rog.
_______________________________________________
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
