Module Cf_smonad

module Cf_smonad: sig .. end

The state monad and its operators.

Overview

The state monad is provided here mostly for reference purposes. It is not actually used directly within the cf library. However, it is sometimes helpful to have an example of the state monad to use when lifting another monad into a new monad with state.

Types

type ('s, 'a) t = 's -> 'a * 's

The state monad. Evaluate by calling it with an initial state.

Modules

module Op: sig .. end

A module containing the ( >>= ) binding operator for composition of state monads.

Operators

val nil : ('s, unit) t

A monad that returns unit and performs no operation.

val return : 'a -> ('s, 'a) t

Use return a to produce a monad that returns a when evaluated.

val load : ('s, 's) t

A monad that returns the encapsulate state.

val store : 's -> ('s, unit) t

Use store s to produce a monad with s as the value of its encapsulated state.

val modify : ('s -> 's) -> ('s, unit) t

Use modify f to produce a monad that applies f to the encapsulated state to obtain a new state value, and which returns the unit value as its result when evaluated.

val field : ('s -> 'a) -> ('s, 'a) t

Use field f to produce a monad that returns the result of applying f to the value of the encapsulated state.