GHC 7.10 regression when using foldr

Malcolm Wallace malcolm.wallace at me.com
Tue Jan 20 11:43:30 UTC 2015


On 20 Jan 2015, at 11:20, Björn Peemöller wrote:

> The reason is the usage of foldr, which changed its type from
>   foldr :: (a -> b -> b) -> b -> [a] -> b -- GHC 7.8.4
> to
>  foldr :: Foldable t => (a -> b -> b) -> b -> t a -> b -- GHC 7.10.1
> Thus, the use of foldr is now ambiguous. I can fix this by providing a
> type signature
>   convert :: ([a], String) -> (List a, String)
> 
> However, is this breaking change intended?

I believe this kind of breakage was predicted by those opposed to the change of signature.  That is not quite the same thing as being intended or desired.

Regards,
    Malcolm



More information about the Glasgow-haskell-users mailing list