hello, i am a bit stuck on the following problem, which seems to be GHC related. consider the following two modules:
{-# OPTIONS -fglasgow-exts -fallow-overlapping-instances #-} module Test where
data T m a = T (m a)
class C m where get :: m a
instance C (T m) instance C m => C (t m)
obs :: T [] Int obs = get
module Test1 where
import Test
obs' :: T [] Int obs' = get
i can load the first one (Test) without problems, but when i load the second one (Test1) a get the error: Test1.hs:6: No instance for (C []) arising from use of `get' at Test1.hs:6 In the definition of `obs'': obs' = get this seems to indicate that the second instance is being used, but i cannot figure out why. am i doing something silly here? -iavor ps: i am not on the GHC users list so please cc me if you replay there -- ================================================== | Iavor S. Diatchki, Ph.D. student | | Department of Computer Science and Engineering | | School of OGI at OHSU | | http://www.cse.ogi.edu/~diatchki | ==================================================