Module Monad.Of_monad

Define a monad through an isomorphism with an existing monad. For example:

type 'a t = { value : 'a }

include Monad.Of_monad (Monad.Ident) (struct
    type nonrec 'a t = 'a t

    let to_monad { value } = value
    let of_monad value = { value }
  end)

Parameters

module Monad : S
module M : sig ... end

Signature

val (>>=) : 'a M.t -> ('a -> 'b M.t) -> 'b M.t

t >>= f returns a computation that sequences the computations represented by two monad elements. The resulting computation first does t to yield a value v, and then runs the computation returned by f v.

val (>>|) : 'a M.t -> ('a -> 'b) -> 'b M.t

t >>| f is t >>= (fun a -> return (f a)).

module Monad_infix : sig ... end
val bind : 'a M.t -> f:('a -> 'b M.t) -> 'b M.t

bind t ~f = t >>= f

val return : 'a -> 'a M.t

return v returns the (trivial) computation that returns v.

val map : 'a M.t -> f:('a -> 'b) -> 'b M.t

map t ~f is t >>| f.

val join : 'a M.t M.t -> 'a M.t

join t is t >>= (fun t' -> t').

val ignore_m : 'a M.t -> unit M.t

ignore_m t is map t ~f:(fun _ -> ()). ignore_m used to be called ignore, but we decided that was a bad name, because it shadowed the widely used Stdlib.ignore. Some monads still do let ignore = ignore_m for historical reasons.

val all : 'a M.t list -> 'a list M.t
val all_unit : unit M.t list -> unit M.t

Like all, but ensures that every monadic value in the list produces a unit value, all of which are discarded rather than being collected into a list.

module Let_syntax : sig ... end

These are convenient to have in scope when programming with a monad: