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Why not?

Name: Anonymous 2011-10-06 13:28



$ ghci

GHCi, version 6.8.2: http://www.haskell.org/ghc/  :? for help

Loading package base ... linking ... done.

Prelude> let yoba a b = if a < b then 123 else "abc"



<interactive>:1:29:

    No instance for (Num [Char])

      arising from the literal `123' at <interactive>:1:29-31

    Possible fix: add an instance declaration for (Num [Char])

    In the expression: if a < b then 123 else "abc"

    In the definition of `yoba':

        yoba a b = if a < b then 123 else "abc"

Prelude>

Name: Anonymous 2011-10-06 14:50

If you really need to do that (which I'm sure you don't), use Either.

yoba :: (Ord a) => a -> a -> Either Int String

yoba a b | a < b     = Left 123

         | otherwise = Right "abc"



f :: (Ord a) => a -> a -> String

f a b = case yoba a b of

            Left _  -> "something"

            Right _ -> "something else"

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Why not?

1 Name: Anonymous 2011-10-06 13:28

11 Name: Anonymous 2011-10-06 14:50

Name: Anonymous 2011-10-06 13:28

Name: Anonymous 2011-10-06 14:50