But then I saw this in an article:

        ($ 3) odd

What does ($ 3) mean? I thought the first argument to ($) is a function?

I checked the type of ($ 3) and it is:

        ($ 3) :: Num a => (a -> b) -> b

I don't understand that. How did that happen? Why can I take a second argument and wrap it in parentheses with ($) and then that second argument pops out and becomes the argument to a function?

I decided to see if other functions behaved similarly. Here is the type signature for the "map" function:

        map :: (a -> b) -> [a] -> [b]

That looks very similar to the type signature for ($). So, I reasoned, I should be able to do the same kind of thing:

        let list=[1,2,3]
        (map list) odd

But that fails. Why? Why does that fail whereas a very similar looking form succeeds when ($) is used?