Re: [Haskell-cafe] bounded ranges

On Jul 23, 2010, at 12:21 AM, Chad Scherrer wrote:

bdRangeSize :: (Ix i, Bounded i) => i -> Int bdRangeSize _ = rangeSize (minBound, maxBound :: i)

Unlike intended, the `i` in the type annotation to `maxBound` is not the same as the `i` in the signature of `bdRangeSize`. You need to enable ScopedTypeVariables and explicitly quantify the type variable `i` in order to refer to it in the annotation of `maxBound`: {-# LANGUAGE ScopedTypeVariables #-} import Data.Ix bdRangeSize :: forall i . (Ix i, Bounded i) => i -> Int bdRangeSize _ = rangeSize (minBound, maxBound :: i) Cheers, Sebastian -- Underestimating the novelty of the future is a time-honored tradition. (D.G.)