Guix

This library provides free monads, which are useful for many tree-like structures and domain specific languages. If f is a Functor then the free Monad on f is the type of trees whose nodes are labeled with the constructors of f. The word "free" is used in the sense of "unrestricted" rather than "zero-cost": Free f makes no constraining assumptions beyond those given by f and the definition of Monad.