On 2016-04-30 at 20:16, Dennis Raddle
main :: IO () main = traverse_ print $ map sin xs
Thanks. I'll see if this works for me. My question right now is, what is traverse_print? Is that the same as
main = traverse print . map sin $ xs
?
I'm guessing IO is traversable and for some reason you don't want to use mapM.
traverse_ is in Data.Foldable [1] You're right that it's closely related to `traverse` and `mapM`. I generally prefer `traverse` and `traverse_` to `mapM` and `mapM_` because they only require Applicative, not Monad. So they work in more cases, and generic code can be more generic. The versions with the _ give back `f ()` instead of `f b` - in this case, we get `IO ()` instead of `IO [()]`. If you try with `traverse, the program won't typecheck, because main needs to have type `IO ()`. bergey Footnotes: [1] http://hackage.haskell.org/package/base-4.8.2.0/docs/Data-Foldable.html#v:tr...