A question about Hugs 98

[Hermo Huguet. Montse]

Hello,
could someone help me?

Using Hugs 98 if I define the following functions:
        
                general f x = f x x
                double = general (+)

The system infers the types:

        general::       (a -> a -> b) -> a -> b
        general (+)::   Num a => a -> a

but
        double::        Integer -> Integer


How is this possible?

Thank you in advance!

>> Montse Hermo