On Wed, Feb 04, 2004 at 02:51:18AM -0800, Malcolm Wallace wrote:
> malcolm 2004/02/04 02:51:18 PST
>
> Modified files:
> src/libraries/base/Data Tree.hs
> Log:
> Exclude functions 'unfoldTreeM' and 'unfoldForestM' in nhc98.
> For some unknown reason they result in a type inference error:
> "No default for Prelude.Monad"
Curious bug (in nhc98) -- it seems you need mutual recursion to trigger it,
as in:
mapM_1 :: Monad m => (a -> m b) -> [a] -> m ()
mapM_1 f [] = return ()
mapM_1 f (x:xs) = f x >> mapM_2 f xs
mapM_2 :: Monad m => (a -> m b) -> [a] -> m ()
mapM_2 f [] = return ()
mapM_2 f (x:xs) = f x >> mapM_1 f xs
Delete either signature and it goes away.
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