[Haskell-beginners] having trouble with helloworld style program

[Ertugrul Soeylemez]

Sunil S Nandihalli <sunil.nandihalli at gmail.com> wrote:

> module Main where
> import Prelude
>
> stringToInt::String->Int
> stringToInt str = read str
>
> main =
>     do x<-getLine
>        y<-stringToInt x
>        print y

It is a type problem.  Using the '<-' syntax for 'stringToInt' requires
that it is a monadic function (like: String -> IO Int), but it is not.
Since it is not monadic, you can simply let-bind the result to a name:

    do xStr <- getLine
       let x = stringToInt xStr
       print x

Or more simply:

    do xStr <- getLine
       print (stringToInt xStr)


Greets,
Ertugrul


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