[Haskell-beginners] fmap Maybe

[Shishir Srivastava]

Hi,

Please can someone explain why these two expression behave differently -

----
fmap (\x -> x) Just 2
Just 2

-----
fmap (\x -> x+2) Just 2

*No instance for (Num (Maybe a0)) arising from a use of `it'*
*In a stmt of an interactive GHCi command: print it*

----
The first expression evaluates fine whereas the second one fails. However
if I do -
----

fmap (\x -> x+2) $ Just 2
Just 4
----

Then the second expression also returns the Maybe value. Why is $ needed in
second expression but not in the first one ?

Thanks,
Shishir
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