What is the easiest way to name a combination of type classes, i.e., to abbreviate the fact that a certain type is an instance of several classes simultaneously? I have a vague sense that this is do-able, but that I am messing up by trying to use an empty class body as below. So in the code below, I try to use FooBar to abbreviate the conjunction of Foo and Bar. But while f (which uses a FooBar constraint) has a valid definition, it can't be used. On the other hand, g (which uses the long-winded constraint), is both a valid defined and useable. (In a real example, imagine that FooBar names a conjunction of a half dozen things, so that the g-like form really is onerous, whereas the f-like form would be sweet and tidy :) .) -- Fritz ------------------- class Foo a where foo :: a -> Int class Bar a where bar :: a -> a class (Foo a, Bar a) => FooBar a f :: FooBar a => a -> Int f a = foo (bar a) g :: (Foo a, Bar a) => a -> Int g a = foo (bar a) instance Foo Char where foo = ord instance Bar Char where bar = id