Tutorial by Topics: monad

A monad is a data type of composable actions. Monad is the class of type constructors whose values represent such actions. Perhaps IO is the most recognizable one: a value of IO a is a "recipe for retrieving an a value from the real world". We say a type constructor m (such as [] or Maybe...

State monads are a kind of monad that carry a state that might change during each computation run in the monad. Implementations are usually of the form State s a which represents a computation that carries and potentially modifies a state of type s and produces a result of type a, but the term &quo...