Greetings Haskellers, I'm running into a problem representing some fairly complicated types, and I'll try to put together a simpler example to get your suggestions. In Paul Hudak's SOE, I find a definition of expression: data Expr = C Float | V String | Expr :+ Expr | Expr :- Expr | Expr :* Expr | Expr :/ Expr Now this is compelling, but sometimes, I might want to have a function that takes a variable only, not just any kind of expression. I could write something like: typeOfVariable :: Expression -> Type typeOfVariable (V s) = ... _ = error... But thats not very satisfying from a type-checking perspective. So it makes sense to create a constructor: data Variable = VVariable String data Expr = C Float | V Variable | Expr :+ Expr | Expr :- Expr | Expr :* Expr | Expr :/ Expr and make typeOfVariable :: Variable -> Type. But then when I want to match or create a variable expression, things are starting to get verbose: case expr of C f -> ... V (Variable (VVariable s)) -> ... ... And if I want a still more accurate hierarchy, the construction and destruction of Variables can really become cumbersome. For an interpreter I'm writing, I found myself writing a function "constructVarExpr :: String -> Expr" just to make it easier. This all seems very inelegant, and I get the feeling that there's a better way to do this. Any suggestions on how I could better represent Expressions or Variables to keep the type-checking but decrease the verbosity? peace, Isaac Jones