Question

This expression:

sort words "fire water earth fire"

— gives this error —

Couldn't match expected type `[a]'
against inferred type `GHC.Base.String -> [GHC.Base.String]'

Could someone explain to me what is going on here and how to elegantly express sort.words?

Answer 1

You want this:

sort (words "fire water earth fire")

when you do

sort words "fire water earth fire"

it’s actually doing

(sort words) "fire water earth fire"

sort expects a list ([a]), but you’re instead giving it words, which is a function takes a string and returns a list of strings (String -> [String]), hence the error message (it can’t treat String -> [String] as a list of anything).

You can also do this:

sort $ words "fire water earth fire"

which is equivalent to the first version and might look neater.