Symbols in Haskell

Question

I have a problem understanding a character in Haskell:

=<< 

how in:

 -- return the last ten lines of a file tail10 = drop =<< subtract 10 . length 

Can someone explain to me what this means?

I also think that this happens a lot when I learn Haskell, so that I come across one of these characters, I have no idea what they mean or how they work. Is there a website or tutorial that goes deeper regarding only characters in Haskell and not the functions themselves?

Answer 1

Here is a list of reserved keywords in Haskell . =<< you are asking about is just a function, so we can request Hoogle . He tells us that =<< is just >>= with the arguments changed. >>= is a fundamental monad function ("monadic composition") that you can read about in many places, including LYAH .