typelits-witnesses (hackage): This library contains:  A small specialized subset of the *singletons* library as it pertains to Nat and Symbol, for when you need some simple functionality without wanting to invoke the entire *singletons* library.  Operations for manipulating these singletons and KnownNat and KnownSymbol instances, such as addition and multiplication of singletons/KnownNat instances.  Operations for the comparison of Nats in a way that works well with  GHC.TypeLits*'s different comparison systems.  This is helpful for bridging together libraries that use different systems; this functionality is not yet provided by *singletons*.
Keywords: data|library|mit