[Haskell-beginners] foldr problem

[akash g]

Or you can try foldr1, which doesn't need a terminating value.

Here's its definition from the Standard Prelude

foldr1                  :: (a -> a -> a) -> [a] -> afoldr1 _ [x]
     =  xfoldr1 f (x:xs)         =  f x (foldr1 f xs)foldr1 _ []
      =  errorEmptyList "foldr1"




On Mon, Mar 3, 2014 at 12:21 PM, Roelof Wobben <r.wobben at home.nl> wrote:

>  Thanks,
>
> This did the job:
>
> import Data.Char
>
> x = foldr max 0 [5,10,2,8,1]
>
> -- Note that comments are preceded by two hyphens
> {- or enclosed
>    in curly brace/hypens pairs. -}
> main = print x
>
> Roelof
>
>
> Emanuel Koczwara schreef op 2-3-2014 22:51:
>
> Hi,
>
> W dniu 02.03.2014 22:44, Roelof Wobben pisze:
>
> Hello,
>
> I now have to use foldr to find the max value in a list.
>
> So I do this:
>
> import Data.Char
>
> x = foldr max [5,10,2,8.1]
> -- Note that comments are preceded by two hyphens
> {- or enclosed
>    in curly brace/hypens pairs. -}
> main = print x
>
> But now I see this error message:
>
> main.hs at 7:8-7:13
>     No instance for (Show ([[t0]] -> [t0])) arising from a use of `print'
> Possible fix: add an instance declaration for (Show ([[t0]] -> [t0])) In
> the expression: print x In an equation for `main': main = print x
>
>
>
>   Please look at foldr type and documentation. There is one argument
> missing in your code.
>
> Regards,
> Emanuel
>
>
>
> _______________________________________________
> Beginners mailing listBeginners at haskell.orghttp://www.haskell.org/mailman/listinfo/beginners
>
>
>
>
> ------------------------------
>    <http://www.avast.com/>
>
> Dit e-mailbericht bevat geen virussen en malware omdat avast! Antivirus<http://www.avast.com/>actief is.
>
>
> _______________________________________________
> Beginners mailing list
> Beginners at haskell.org
> http://www.haskell.org/mailman/listinfo/beginners
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.haskell.org/pipermail/beginners/attachments/20140303/27b7c953/attachment.html>