Re: [Haskell-cafe] Usage of Read Class

I would like to ask something that results in when I have the following commands data Color = Red | Green | Blue | Indigo | Violet deriving (Enum,Show,Read) (read.show) x

<interactive>:1:1: Ambiguous type variable `a' in the constraint: `Read a' arising from a use of `read' at <interactive>:1:1-4 Probable fix: add a type signature that fixes these type variable(s)

What the error message says is, it doesn't know which type to read to. read has the type Read a => String -> a, and unless you tell it what 'a' is going to be, how would it know? If you say '(read.show) x :: Color' it should work just fine. Cheers, /Niklas