I had a play today and managed to figure out how to write the code I needed. If anyone is curious the resulting code is: {-# LANGUAGE TemplateHaskell #-} module Template where import Language.Haskell.TH typeChecker :: String -> Q Exp typeChecker schemeType = do x <- newName "x" return $ LamE [VarP x] (CaseE (VarE x) [Match (ConP ty [WildP]) (NormalB (AppE (ConE bool) (ConE true))) [],Match WildP (NormalB (AppE (ConE bool) (ConE false))) []]) where ty = mkName schemeType bool = mkName "Bool" true = mkName "True" false = mkName "False" I then import this module into where I am defining the predicates (templates have to be defined in a seperate module), where the code becomes: numberP :: SchemeVal -> SchemeVal numberP = $(typeChecker "Number") boolP :: SchemeVal -> SchemeVal boolP = $(typeChecker "Bool") symbolP :: SchemeVal -> SchemeVal symbolP = $(typeChecker "Symbol") So, as I always knew, not really worth the effort as I've written a 13 line module to save 3 lines of code, but a good learning experience =) Thanks again for the point in the right direction. Cheers, Matt