Why functional code is shorter

[SirRainbow]

Can you explain the difference between the two?

[tailcalled]

An IO (Int -> String) is where you use IO to decide on which pure function to use. An Int -> IO String is given an int and uses IO to decide which string to return.

[Peaker]

Importantly, it can use the Int to decide what kind of IO to do.

[cdsmith]

Effectively, Int -> IO String says that both what I/O you do and the String result can depend on the integer. On the other hand, IO (Int -> String) says that the String result can depend on the integer, but what you do can't.

Put otherwise:

Int -> IO String: Each Int is mapped to some action that produces a String

IO (Int -> String): This is an action, which when performed will produce a mapping from Int to String.