[Haskell-beginners] Exposing Ratio data constructor

Hej hej! I was writing some code using Ratio, and even though I know it's tucked behind an abstraction barrier, I really wanted access to the Ratio data constructor ':%'. I wrote invertRatio like such: invertRatio r = denominator r % numerator But I really wanted to write it like this: invertRatio (n :% d) = d % n I understand that exposing ':%' causes problems, since it allows us not only to pick apart ratios, but to construct bad ones that would normally be caught when constructed with '%'. (Such as '1:%0'.) Is there any way to avoid this, while still letting the user benefit from the nice pattern matching syntax that exposing the data constructor allows? Kram, Casey Rodarmor