lennart:
Yes, I think we want Integer to be the type that is used unless you ask for something else. It adheres to the principle of getting it right before optimizing.
On a similar note, there's been a long discussion in #haskell about the problems of defaulting to floating point, and should Rational, or something similar be used instead, given that Doubles and Float are broken for a lot of basic things (like Eq and Ord), much as we default to Integer already. The issues raised regarding Rational was that you can unexpectedly build up large precision, and performance in general, of course. It was unknown whether there were suitable replacement types. Rational also can't be used with Floating functionsl, like sqrt, which would bring back Double defaulting. But shouldn't this really work in Haskell, and if you want imprecision you must ask for Double explicitly: Prelude> 1.1 + 2.2 - 3.3 4.440892098500626e-16 Prelude> 1.1 + 2.2 - 3.3 :: Rational 0%1 -- Don