Confusion with in-built toLower function-CodePudding

I am using VSCode as my IDE for Haskell on a Mac.

This simple function

toLowerSt :: String -> String
toLowerSt = map toLower

returns the following error:

Main.hs:92:17: error:
    • Variable not in scope: toLower :: Char -> Char
    • Perhaps you meant ‘toLowerSt’ (line 92)
   |
92 | toLowerSt = map toLower
   |                 ^^^^^^^
Failed, no modules loaded.

I struggle to understand what the actual problem here is. A string is mapped into chars yet it's throwing me this error.

CodePudding user response：

The toLower :: Char -> Char function is defined in the Data.Char module and not re-exported by the Prelude, you thus need to import this with:

import Data.Char(toLower)

toLowerSt :: String -> String
toLowerSt = map toLower