On Sun, Apr 6, 2014, at 10:39 AM, Karl Voelker wrote: > data StringIndex = S1 | S2 | S3 | S4 | S5 | S6 deriving (Eq, Ord, Enum, > Bounded, Read, Show) I should have included the Ix class in the deriving list, so you can use it as an Array index. -Karl