Module `React.S`

include module type of React.S

Primitive and basics

type 'a t = 'a React.signal

The type for signals of type 'a.

val retain : 'a React.signal -> (unit -> unit) -> [ `R of unit -> unit ]

retain s c keeps a reference to the closure c in s and returns the previously retained value. c will never be invoked.

Raises. Invalid_argument on constant signals.

val stop : ?strong:bool -> 'a React.signal -> unit

stop s, stops updating s. It conceptually becomes const with the signal's last value and cannot be restarted. Allows to disable effectful signals.

The strong argument should only be used on platforms where weak arrays have a strong semantics (i.e. JavaScript). See details.

Note. If executed in an update step the signal may still update in the step.

val equal : 
  ?eq:('a -> 'a -> bool) ->
  'a React.signal ->
  'a React.signal ->
  bool

equal s s' is true iff s and s' are equal. If both signals are constant eq is used between their value (defauts to structural equality). If both signals are not constant, physical equality is used.

val trace : ?iff:bool t -> ('a -> unit) -> 'a React.signal -> 'a React.signal

trace iff tr s is s except tr is invoked with s's current value and on s changes when iff is true (defaults to S.const true). For all t where [s]_t = v and (t = 0 or ([s]_t-dt= v' and eq v v' = false)) and [iff]_t = true, tr is invoked with v.

From events

val hold : ?eq:('a -> 'a -> bool) -> 'a -> 'a React.event -> 'a React.signal

hold i e has the value of e's last occurrence or i if there wasn't any.

[hold i e]_t = i if [e]_<=t = None
[hold i e]_t = v if [e]_<=t = Some v

Transforming and filtering

val app : 
  ?eq:('b -> 'b -> bool) ->
  ('a -> 'b) React.signal ->
  'a React.signal ->
  'b React.signal

app sf s holds the value of sf applied to the value of s, [app sf s]_t = [sf]_t [s]_t.

val filter : 
  ?eq:('a -> 'a -> bool) ->
  ('a -> bool) ->
  'a ->
  'a React.signal ->
  'a React.signal

filter f i s is s's values that satisfy p. If a value does not satisfy p it holds the last value that was satisfied or i if there is none.

[filter p s]_t = [s]_t if p [s]_t = true.
[filter p s]_t = [s]_t' if p [s]_t = false and t' is the greatest t' < t with p [s]_t' = true.
[filter p e]_t = i otherwise.

val diff : ('a -> 'a -> 'b) -> 'a React.signal -> 'b React.event

diff f s is an event with occurrences whenever s changes from v' to v and eq v v' is false (eq is the signal's equality function). The value of the occurrence is f v v'.

[diff f s]_t = Some d if [s]_t = v and [s]_t-dt = v' and eq v v' = false and f v v' = d.
[diff f s]_t = None otherwise.

val changes : 'a React.signal -> 'a React.event

changes s is diff (fun v _ -> v) s.

val sample : 
  ('b -> 'a -> 'c) ->
  'b React.event ->
  'a React.signal ->
  'c React.event

sample f e s samples s at e's occurrences.

[sample f e s]_t = Some (f ev sv) if [e]_t = Some ev and [s]_t = sv.
[sample e s]_t = None otherwise.

val on : 
  ?eq:('a -> 'a -> bool) ->
  bool React.signal ->
  'a ->
  'a React.signal ->
  'a React.signal

on c i s is the signal s whenever c is true. When c is false it holds the last value s had when c was the last time true or i if it never was.

[on c i s]_t = [s]_t if [c]_t = true
[on c i s]_t = [s]_t' if [c]_t = false where t' is the greatest t' < t with [c]_t' = true.
[on c i s]_t = i otherwise.

val when_ : 
  ?eq:('a -> 'a -> bool) ->
  bool React.signal ->
  'a ->
  'a React.signal ->
  'a React.signal

deprecated
Use on.

val dismiss : 
  ?eq:('a -> 'a -> bool) ->
  'b React.event ->
  'a ->
  'a React.signal ->
  'a React.signal

dismiss c i s is the signal s except changes when c occurs are ignored. If c occurs initially i is used.

[dismiss c i s]_t = [s]_t' where t' is the greatest t' <= t with [c]_t' = None and [s]_t'-dt <> [s]_t'
[dismiss_ c i s]₀ = v where v = i if [c]₀ = Some _ and v = [s]₀ otherwise.

Accumulating

val accum : 
  ?eq:('a -> 'a -> bool) ->
  ('a -> 'a) React.event ->
  'a ->
  'a React.signal

accum e i is S.hold i (E.accum e i).

val fold : 
  ?eq:('a -> 'a -> bool) ->
  ('a -> 'b -> 'a) ->
  'a ->
  'b React.event ->
  'a React.signal

fold f i e is S.hold i (E.fold f i e).

Combining

val bind : 
  ?eq:('b -> 'b -> bool) ->
  'a React.signal ->
  ('a -> 'b React.signal) ->
  'b React.signal

bind s sf is switch (map ~eq:( == ) sf s).

val fix : 
  ?eq:('a -> 'a -> bool) ->
  'a ->
  ('a React.signal -> 'a React.signal * 'b) ->
  'b

fix i sf allow to refer to the value a signal had an infinitesimal amount of time before.

In fix sf, sf is called with a signal s that represents the signal returned by sf delayed by an infinitesimal amount time. If s', r = sf s then r is returned by fix and s is such that :

[s]_t = i for t = 0.
[s]_t = [s']_t-dt otherwise.

eq is the equality used by s.

Raises. Invalid_argument if s' is directly a delayed signal (i.e. a signal given to a fixing function).

Note. Regarding values depending on the result r of s', r = sf s the following two cases need to be distinguished :

After sf s is applied, s' does not depend on a value that is in a step and s has no dependents in a step (e.g in the simple case where fix is applied outside a step).
In that case if the initial value of s' differs from i, s and its dependents need to be updated and a special update step will be triggered for this. Values depending on the result r will be created only after this special update step has finished (e.g. they won't see the i of s if r = s).
Otherwise, values depending on r will be created in the same step as s and s' (e.g. they will see the i of s if r = s).

Lifting

Lifting combinators. For a given n the semantics is :

[ln f a1 ... an]_t = f [a1]_t ... [an]_t

val l1 : 
  ?eq:('b -> 'b -> bool) ->
  ('a -> 'b) ->
  'a React.signal ->
  'b React.signal

The following modules lift some of Stdlib functions and operators.

module Bool : sig ... end

module Int : sig ... end

module Float : sig ... end

module Pair : sig ... end

module Option : sig ... end

module Compare : sig ... end

Combinator specialization

Given an equality function equal and a type t, the functor Make automatically applies the eq parameter of the combinators. The outcome is combinators whose results are signals with values in t.

Basic types are already specialized in the module Special, open this module to use them.

module type EqType = sig ... end

Input signature of Make

module type S = sig ... end

Output signature of Make

module Make (Eq : EqType) : S with type 'a v = 'a Eq.t

Functor specializing the combinators for the given signal value type

module Special : sig ... end

Specialization for booleans, integers and floats.

include Shared_sigs.S with type 'a t := 'a t and type 'a sv := 'a Value.t

val const : 'a -> 'a t

val value : 'a t -> 'a Value.t

val map : ?eq:('b -> 'b -> bool) Value.t -> ('a -> 'b) Value.t -> 'a t -> 'b t

val fmap : 
  ?eq:('b -> 'b -> bool) Value.t ->
  ('a -> 'b option) Value.t ->
  'b Value.t ->
  'a t ->
  'b t

val merge : 
  ?eq:('a -> 'a -> bool) Value.t ->
  ('a -> 'b -> 'a) Value.t ->
  'a ->
  'b t list ->
  'a t

val l2 : 
  ?eq:('c -> 'c -> bool) Value.t ->
  ('a -> 'b -> 'c) Value.t ->
  'a t ->
  'b t ->
  'c t

val l3 : 
  ?eq:('d -> 'd -> bool) Value.t ->
  ('a -> 'b -> 'c -> 'd) Value.t ->
  'a t ->
  'b t ->
  'c t ->
  'd t

val l4 : 
  ?eq:('e -> 'e -> bool) Value.t ->
  ('a -> 'b -> 'c -> 'd -> 'e) Value.t ->
  'a t ->
  'b t ->
  'c t ->
  'd t ->
  'e t

val l5 : 
  ?eq:('f -> 'f -> bool) Value.t ->
  ('a -> 'b -> 'c -> 'd -> 'e -> 'f) Value.t ->
  'a t ->
  'b t ->
  'c t ->
  'd t ->
  'e t ->
  'f t

val l6 : 
  ?eq:('g -> 'g -> bool) Value.t ->
  ('a -> 'b -> 'c -> 'd -> 'e -> 'f -> 'g) Value.t ->
  'a t ->
  'b t ->
  'c t ->
  'd t ->
  'e t ->
  'f t ->
  'g t

val switch : ?eq:('a -> 'a -> bool) Value.t -> 'a t t -> 'a t

module Infix : sig ... end

Infix operators

module Lwt : sig ... end

Cooperative versions of the React operators

val create : 
  ?eq:('a -> 'a -> bool) ->
  ?default:('a t * (?step:React.step -> 'a -> unit)) option ->
  ?reset_default:bool ->
  'a ->
  'a React.signal * (?step:React.step -> 'a -> unit)

create ?eq ?default ?reset_default x produces a pair s, f, where s is a reactive signal, and f is a function for updating the signal.

The initial value of the signal is x, unless default is provided. default, if provided, is used as the signal. reset_default, if set to true (default: false), resets the value of default to x.