[Haskell-cafe] interval arithmetic for integers?

I'm looking to not reinvent the wheel. Is there an existing package that supports interval arithmetic on integers (or more)? A possible complication is that I'm hoping to include open intervals such as (GreaterEqThan 3). If there's not a package to go with, any pointers on the appopriate rules for this stuff? I started coding up multiplication and decided it was harder than I first thought... Thanks for your time, Nick