package monads

  1. Overview
  2. Docs
package monads
Legend:
Library
Module
Module type
Parameter
Class
Class type

The option aka Maybe monad.

This monad can be used to denote partial computations or a limited form of non-deterministic computations where an absence of result, i.e., the bottom value, can be considered as a possible outcome.

module type S = sig ... end

The unary option monad.

module type S2 = sig ... end

The binary option monad

include S with type 'a t = 'a option and type 'a m = 'a and type 'a e = 'a option
include Trans.S with type 'a t = 'a option with type 'a m = 'a with type 'a e = 'a option
type 'a t = 'a option
type 'a m = 'a
type 'a e = 'a option
val lift : 'a m -> 'a t

lifts inner monad into the resulting monad

val run : 'a t -> 'a e

runs the computation

include Monad with type 'a t := 'a t
val void : 'a t -> unit t

void m computes m and discrards the result.

val sequence : unit t list -> unit t

sequence xs computes a sequence of computations xs in the left to right order.

val forever : 'a t -> 'b t

forever xs creates a computationt that never returns.

module Fn : sig ... end

Various function combinators lifted into the Kleisli category.

module Pair : sig ... end

The pair interface lifted into the monad.

module Triple : sig ... end

The triple interface lifted into a monad.

module Lift : sig ... end

Lifts functions into the monad.

module Exn : sig ... end

Interacting between monads and language exceptions

module Collection : sig ... end

Lifts collection interface into the monad.

module List : Collection.S with type 'a t := 'a list

The Monad.Collection.S interface for lists

module Seq : Collection.S with type 'a t := 'a Core_kernel.Sequence.t

The Monad.Collection.S interface for sequences

include Syntax.S with type 'a t := 'a t
val (>=>) : ('a -> 'b t) -> ('b -> 'c t) -> 'a -> 'c t

f >=> g is fun x -> f x >>= g

val (!!) : 'a -> 'a t

!!x is return x

val (!$) : ('a -> 'b) -> 'a t -> 'b t

!$f is Lift.unary f

val (!$$) : ('a -> 'b -> 'c) -> 'a t -> 'b t -> 'c t

!$$f is Lift.binary f

val (!$$$) : ('a -> 'b -> 'c -> 'd) -> 'a t -> 'b t -> 'c t -> 'd t

!$$$f is Lift.ternary f

val (!$$$$) : ('a -> 'b -> 'c -> 'd -> 'e) -> 'a t -> 'b t -> 'c t -> 'd t -> 'e t

!$$$$f is Lift.quaternary f

val (!$$$$$) : ('a -> 'b -> 'c -> 'd -> 'e -> 'f) -> 'a t -> 'b t -> 'c t -> 'd t -> 'e t -> 'f t

!$$$$$f is Lift.quinary f

include Syntax.Let.S with type 'a t := 'a t
val let* : 'a t -> ('a -> 'b t) -> 'b t

let* r = f x in b is f x >>= fun r -> b

val and* : 'a t -> 'b t -> ('a * 'b) t

monoidal product

val let+ : 'a t -> ('a -> 'b) -> 'b t

let+ r = f x in b is f x >>| fun r -> b

val and+ : 'a t -> 'b t -> ('a * 'b) t

monoidal product

include Core_kernel.Monad.S with type 'a t := 'a t
val (>>=) : 'a t -> ('a -> 'b t) -> 'b t
val (>>|) : 'a t -> ('a -> 'b) -> 'b t
module Monad_infix : sig ... end
val bind : 'a t -> f:('a -> 'b t) -> 'b t
val return : 'a -> 'a t
val map : 'a t -> f:('a -> 'b) -> 'b t
val join : 'a t t -> 'a t
val ignore_m : 'a t -> unit t
val all : 'a t list -> 'a list t
val all_unit : unit t list -> unit t
module Let_syntax : sig ... end
module Let : Syntax.Let.S with type 'a t := 'a t

Monadic operators, see Monad.Syntax.S for more.

module Syntax : Syntax.S with type 'a t := 'a t

Monadic operators, see Monad.Syntax.S for more.

include Choice.S with type 'a t := 'a t
include Choice.Basic with type 'a t := 'a t
val pure : 'a -> 'a t

pure x creates a computation that results in x.

val accept : 'a -> 'a t

accept x accepts x as a result of computation. (Same as pure x.

val reject : unit -> 'a t

reject () rejects the rest of computation sequence, and terminate the computation with the zero result (Same as zero ()

val guard : bool -> unit t

guard cond ensures cond is true in the rest of computation. Otherwise the rest of the computation is rejected.

val on : bool -> unit t -> unit t

on cond x computes x only iff cond is true

val unless : bool -> unit t -> unit t

unless cond x computes x unless cond is true.

include Plus.S with type 'a t := 'a t
val zero : unit -> 'a t

zero () constructs a zero element

val plus : 'a t -> 'a t -> 'a t

plus x y an associative operation.

include Fail.S with type 'a t := 'a t and type 'a error = unit
type 'a error = unit

a type of error

val fail : _ error -> 'a t

fail err diverges the computation, possibly providing an extra information in a value of type _ error.

val catch : 'a t -> (_ error -> 'a t) -> 'a t

catch m f if m diverges with some bottom value err, the f err is a result of the whole computation, otherwise returns m.

module T1 (M : Core_kernel.T1) : sig ... end
module T2 (M : Core_kernel.T2) : sig ... end
module Make (M : Monad) : S with type 'a m := 'a T1(M).m and type 'a t := 'a T1(M).t and type 'a e := 'a T1(M).e

Make(M) composes the option monad with the monad M.

module Make2 (M : Monad2) : S2 with type ('a, 'e) t := ('a, 'e) T2(M).t and type ('a, 'e) m := ('a, 'e) T2(M).m and type ('a, 'e) e := ('a, 'e) T2(M).e

Make2(M) composes the option monad with the monad M.

OCaml

Innovation. Community. Security.

GitHub Discord Twitter Peertube RSS
About
Changelog Releases Industrial Users Academic Users Why OCaml
Ecosystem
Packages Community Events OCaml Planet Jobs
Resources
Install OCaml Get Started Platform Tools Language Manual Standard Library API Books Exercises Papers OCaml Playground Logo
Policies
Carbon Footprint Governance Privacy Code of Conduct