Any applicative functor can be given numeric instances in a boilerplate way. The applicative-numbers package provides an include file that makes it a snap to define these instances.
Besides this wiki page, here are more ways to find out about applicative-numbers:
- Visit the Hackage page for library documentation and to download & install.
- Or install with cabal install applicative-numbers.
- Get the code repository: darcs get http://code.haskell.org/~conal/code/applicative-numbers.