Parenthesis are not really optional, they're just used differently than other languages. Other languages use parenthesis for function application and grouping, in Haskell it's just grouping.

    wordsPerLine = filter (>0) . map (length . words) . lines

Funnily enough, parenthesis are actually optional in Elixir, although it's a warning to use pipe syntax without them. The following is valid in both Haskell and Elixer:

    length [1,2,3]

Whenever you see something like

  apply foo bar (lol wat)

in Haskell, and it confuses you, simply mentally replace it with

  apply(foo, bar, lol(wat))

To translate into a more popular syntax (e.g. JavaScript).

Problem solved:

    strSum = sum . parsed . words
             where
                parsed = map read