[Haskell-beginners] IO String and String using readFile
ian at zenhack.net
Wed Mar 27 03:57:13 UTC 2019
Sounds like you want concatMap:
Quoting Yugesh Kothari (2019-03-26 23:48:35)
> I see. anyway, my use case is something like this-
> I have two functions
> fromFile :: [String] -> [Int]
> func :: String -> [Int]
> I want to use the "words contents" output and pass each element in it
> to func and send back [Int] from "fromFile" function (where I
> originally read the file.)
> Could you suggest a better way to do this?
> Quoting� Ian Denhardt
> On Wed, 27 Mar, 2019, 9:13 AM Ian Denhardt, <ian at zenhack.net> wrote:
> It would help to see the complete source file, but I'll hazard a
> you're doing something like:
> main = do
> � � contents <- readFile "file.txt"
> � � words contents
> At the GHCi prompt, each line can be any expression, and GHCi will
> evaluate it and then display it. The two lines in your session
> really related.
> In contrast, the do block in the source file expects the expression
> the end to be an IO action.
> What do you want your program to do when you get to "words
> display it? (If you want to display it, pass it to `print`).
> Quoting Yugesh Kothari (2019-03-26 23:35:14)
> >� � Hi,�
> >� � I am trying to read data from a file.
> >� � When I do-
> >� � ghci> contents <- readFile "file.txt"
> >� � ghci> words contents
> >� � Then everything works.
> >� � The same thing when done in a .hs file gives an IO String vs
> >� � error.
> >� � Why is that so?
> 1. mailto:ian at zenhack.net
More information about the Beginners