Question

My code:

import System.IO

main :: IO()
main = do
inFile <- openFile "file.txt" ReadMode
content <- hGetContents inFile
let
    someValue = someFunction(content)
    in
    print(anotherFunction(someValue))
    print(anotherFunction2(someValue))
hClose inFile

My error:

- Type error in application
*** Expression     : print (anotherFunction2(someValue))
*** Term           : print
*** Type           : e -> IO ()
*** Does not match : a -> b -> c -> d

I need to print two or more lines with functions that require “someValue”.
How I can fix it?

Answer 1

When you use let binding in a do block, don’t use the in keyword.

main :: IO()
main = do
    inFile <- openFile "file.txt" ReadMode
    content <- hGetContents inFile
    let someValue = someFunction(content)
    print(anotherFunction(someValue))
    print(anotherFunction2(someValue))
    hClose inFile