On Mon, 22 Feb 2010 23:02:13 +0100, Iustin Pop
Hi there,
I'm trying to upgrade some code to ghc 6.12 but under -Wall, the new warning about unused do binds is triggering on Text.Printf.printf usage.
This code:
import Text.Printf
main :: IO () main = do printf "Hello, world\n" printf "Hello the second time\n"
When run with runhaskell -Wall gives:
Warning: A do-notation statement discarded a result of type GHC.Prim.Any. Suppress this warning by saying "_ <- printf "Hello, world\n"", or by using the flag -fno-warn-unused-do-bind.
Now, I'm confused why such a simple usage of printf triggers this warning; enforcing the first printf to type IO () fixes the warning, but it seems strange to no longer be able to simply write printf.
Anyone knows a workaround, or can enlighten me what I'm doing wrong?
What about providing a printf_ function with "IO ()" as return type? (like mapM vs mapM_) -- Nicolas Pouillard http://nicolaspouillard.fr