Some ways to fix the given code: strlen :: IO () strlen = do putStr "Enter a string: " >> do xs <- getLine putStr "The string has " putStr (show (length xs)) putStr " characters" strlen :: IO () strlen = do putStr "Enter a string: " do xs <- getLine putStr "The string has " putStr (show (length xs)) putStr " characters" strlen :: IO () strlen = do putStr "Enter a string: " xs <- getLine putStr "The string has " putStr (show (length xs)) putStr " characters" On 15/05/2018 18:13, Sylvester via Haskell-Cafe wrote:
strlen in Hutton 2ed 10.5 Derived primitives => run on Windows 7 Haskell Platform 8.2.2 strlen :: IO () strlen = do putStr "Enter a string: " xs <- getLine putStr "The string has " putStr (show (length xs)) putStr " characters" =================================================== GHCi, version 8.2.2: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( C:\strlen.WhiteSpaced.hs, interpreted )
C:\strlen.WhiteSpaced.hs:2:14: error: Parse error in pattern: putStr Possibly caused by a missing 'do'? | 2 | strlen = do putStr "Enter a string: " | ^^^^^^^^^^^^^^^^^^^^^^^^^^^... Failed, no modules loaded. Prelude> ================================================== strlen :: IO () strlen = do {putStr "Enter a string: "; xs <- getLine; putStr "The string has "; putStr (show (length xs)); putStr " characters"} ================================================= GHCi, version 8.2.2: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( C:\strlen.Bracesed.hs, interpreted ) Ok, one module loaded. *Main>
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