many times I ended up in writing following combinators, I think it would add some value if library has it :

1. F<A, Bool> and(F<A, Bool> pred1, F<A, Bool> pred2)
2. F<A, Bool> or(F<A, Bool> pred1, F<A, Bool> pred2)
3. F < B, Bool > comap(F<B, A>, F<A, Bool>)
4. F<B, Bool> notFor(F<B, A>, F<A, Bool>) [a la Haskell's Data.Function.Predicate's isn't]
5. F<A, Bool> inverse(F<A, Bool>)

additionally we could add:
nand, nor, xor
We can also implement Predicate2<A, B>, Predicate3<A, B, C> and so on.
thoughts?