[Haskell-beginners] GHC 6.12, -fwarn-unused-do-bind and Text.Printf

[Roel van Dijk]

On Mon, Feb 22, 2010 at 11:02 PM, Iustin Pop <iusty at k1024.org> wrote:
> A side question would be why we have "instance PrintfType (IO a)"
> instead of "instance PrintfType (IO ())"; what use is there for that
> generic type? Can printf return anything else than IO () (when used
> under IO at all)?

I can only guess, but perhaps because "instance PrintfType (IO ())"
would require the FlexibleInstances language extension. I believe the
current implementation of printf is fully Haskell98.