Put simply, . is function composition, just like in math: f (g x) = (f . g) x In your case, you are creating a new function, sumEuler that could also be defined like this: sumEuler x = sum (map euler (mkList x)) The style in your example is called “point-free” style — the arguments … Read more
I guess I can answer this from authority. Is there a reason for using the books way that is much better than using all ($) symbols? There’s no special reason. Bryan and I both prefer to reduce line noise. . is quieter than $. As a result, the book uses the f . g . … Read more
The $ operator is for avoiding parentheses. Anything appearing after it will take precedence over anything that comes before. For example, let’s say you’ve got a line that reads: putStrLn (show (1 + 1)) If you want to get rid of those parentheses, any of the following lines would also do the same thing: putStrLn … Read more