[Haskell-beginners] Reading input
cmb21 at kent.ac.uk
Wed Aug 20 16:38:33 EDT 2008
Or, call median with your list of ints and forget about mainProg...:)
On Wed, 20 Aug 2008, C.M.Brown wrote:
> On another note, you may want to avoid monads altogether for this. You can
> run this straight from ghci (replacing mainProg with main)
> mainProg :: [Int] -> Int
> mainProg arg = median lst
> and then call mainProg with your desired list of stings
> > mainProg [1,2,3,4]
> On Wed, 20 Aug 2008, Yitzchak Gale wrote:
> > Hi Barry,
> > Barry Burd wrote:
> > > median :: [Int] -> Int
> > > median lst =
> > > case medians lst of
> > > -- All the values in the result are the same, we just pick the first one
> > > x:xs -> x
> > >
> > > main = do
> > > putStr "Enter a list: "
> > > lst <- getLine
> > > median lst
> > > I'm sure this is because Haskell isn't automatically changing a String
> > > to a List of numbers. But how can I do this?
> > Use the "read" function. Watch out, though - there is
> > no error checking there. So if the user enters a string
> > that does not have the right syntax for a Haskell list
> > of integers, your program will halt with an error message.
> > You have another problem - you used the "median"
> > function as a step in a do block - but each step in a
> > do block must have type "IO a" for some type a.
> > Here's how you could write your main function:
> > main = do
> > putStr "Enter a list: "
> > lst <- getLine
> > print $ median $ read lst
> > Regards,
> > Yitz
> > _______________________________________________
> > Beginners mailing list
> > Beginners at haskell.org
> > http://www.haskell.org/mailman/listinfo/beginners
> Beginners mailing list
> Beginners at haskell.org
More information about the Beginners