[Haskell-cafe] Distributing monadic(?) functions across dyadic functions

Is there a common way (standard libs, higher order) to express the lambda part below? It's not particulary complicated but I think it is not higher-order enough

unionBy (\x y -> fst x == fst y) listOfPairs1 listOfPairs2

Something like "distribute fst (==)" where

distribute f op x y = f x `op` f y

would leave

unionBy (distribute fst (==)) listOfPairs1 listOfPairs2

I imagine something involving Arrows and/or zip/curry/uncurry but I just can't see it. Is this a case of trying to make something more complicated than it is? Jared. -- http://www.updike.org/~jared/ reverse ")-:"