| The error in linux is: | Illegal instance declaration for `Read (UArray Int Double)' | (The instance type must be of form (T a b c) | where T is not a synonym, and a,b,c are distinct type variables) | In the instance declaration for `Read (UArray Int Double)' | | Why does it want three parameters for the instance type? I am baffled by | this. It's saying that in Haskell 98 you can have instance Read (UArray a b) (for type variables a, b) but not instance Read (UArray Int Double) (As Spencer says, use -fglasgow-exts to lift the H98 restriction.) However, you mis-read the error message to say "the instance type must have three parameters", which isn't what I meant at all! I was trying to use an example of the general form, but conveyed the wrong idea. I can see why you read it that way. Now you understand, can you give me a better error message? Thanks Simon