package bap-std

  1. Overview
  2. Docs
package bap-std
Legend:
Library
Module
Module type
Parameter
Class
Class type

State monad. See State for more info.

module type S = sig ... end

State monad interface.

include S with type 'a result = 'a
type ('a, 's) t

('a,'s) t computation that evaluates to 'a and state 's

type 'a result = 'a

'a result is a type that represents result of computation.

include Core_kernel.Std.Monad.S2 with type ('a, 's) t := ('a, 's) t
val (>>=) : ('a, 'e) t -> ('a -> ('b, 'e) t) -> ('b, 'e) t
val (>>|) : ('a, 'e) t -> ('a -> 'b) -> ('b, 'e) t
module Let_syntax : sig ... end
module Monad_infix : sig ... end
val bind : ('a, 'e) t -> ('a -> ('b, 'e) t) -> ('b, 'e) t
val return : 'a -> ('a, 'b) t
val map : ('a, 'e) t -> f:('a -> 'b) -> ('b, 'e) t
val join : (('a, 'e) t, 'e) t -> ('a, 'e) t
val ignore_m : ('a, 'e) t -> (unit, 'e) t
val all : ('a, 'e) t list -> ('a list, 'e) t
val all_ignore : (unit, 'e) t list -> (unit, 'e) t
val put : 's -> (unit, 's) t

put s creates a computation that has effect s and unit value. This operation effectively updates the state by overriding the existent one with the new one. An imperative counterpart of this operation is a statement that performs side effect, e.g., 

put x

is somewhat equivalent to

let state = ref init
let put x = state := x

except that state is not hidden in the language heap, but is reified into a value of type 's.

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

get () creates a computation that evalates to a value, that holds the state. This operation extracts the state, and gives an access for it. The get () is somewhat equivalent to the imperative operator (!), i.e.,

let state = ref init
let get () = !state
val gets : ('s -> 'r) -> ('r, 's) t

gets f is a computation whose value is f state)

update f is get () >>= fun s -> put (f s)

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

update f is get () >>= fun s -> put (f s)

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

modify c f is a computation with state f, where s is c >>= get (), i.e., an effect of computation c.

Running state computations.

val run : ('a, 's) t -> 's -> ('a * 's) result

run c init runs computation c with initial state init. Result contains a pair of the computation result and total effect.

val eval : ('a, 's) t -> 's -> 'a result

eval c init contains a value computed by computation c under initial state init.

val exec : ('a, 's) t -> 's -> 's result

exec c init contains an final effect produced by a computation c under initial state init.

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