Module Monad.Trans

Monad Transformer Interface.

A monad transformer is a monad composition operator. There is not notion of a generic transformer, that takes two arbitrary monads and compose them, but every single monad should provide its own transformer. This module provides three interfaces of the transfomers:

• Monad.Trans.S composes two unary monad;
• Monad.Trans.S composes unary and binary monads;
• Monad.Trans.S composes two binary monad;

A composition of two monads denoted as module M = Outer.Make(Inner) can is a new monad M that has properties of both Outer and Inner (you visualize this composition as a russian doll). All transfomers provide a lift function that lifts computations in the inner monad _ m to the resultint monad _ t. The run function will actually run the computation and result in a value of type _ e that each monad transfomer defines differently.