What is the difference between mapM_ and mapM in Haskell?

Question

I\'ve already checked Hoogle, http://hackage.haskell.org/package/base-4.7.0.1/docs/Prelude.html#v:mapM, which says that mapM_ ignores the results.

However,

Answer 1

mapM_ ignores the result. This means, that no return value will be returned. You can see this in interactive mode:

Prelude> mapM (putStrLn . show) [1,2]
1
2
[(),()]
Prelude> mapM_ (putStrLn . show) [1,2]
1
2