React, Functional Reactive Programming for Ocaml

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React, Functional Reactive Programming for OCaml Daniel Bünzli, freelance programmer http://erratique.ch daniel.buenzl [email protected] 1 FRP What & Why Reactive vs. Transforma- tional Functional vs. Imperative Reactive with callbacks and side-effects A counter example let duration = ref 60 let elapsed = ref 0 Callback joy let () = let on_trigger () = elapsed := min (!elapsed + 1) !duration; notify_elapsed_changed () in Timer.each_second ~on_trigger let duration_stepper = let on_change v = duration := v; elapsed := min !elapsed !duration; notify_duration_changed (); notify_elapsed_changed (); in Stepper.create ~value:!duration ~on_change let restart_button = let on_click () = elapsed := 0; notify_elapsed_changed () in Button.create ~on_click Functional Functional Reactive Animation, ICFP'97 Conal Elliott & Paul Hudak Signals & Events type 'a signal = 'a S.t ≈ time -> 'a type 'a event = 'a E.t ≈ time -> 'a option Combinators ! val E.map : ('a -> 'b) -> 'a E.t -> 'b E.t val S.map : ('a -> 'b) -> 'a S.t -> 'b S.t val S.hold : 'a -> 'a E.t -> 'a S.t ... FRP joy let restart : unit E.t = RButton.create () let duration : int S.t = RStepper.create ~value:60 let secs : int S.t = RTimer.seconds () let elapsed : int S.t = let restart_t : int E.t = S.sample (fun _ t -> t) restart secs in let t0 : int S.t = S.hold (S.value secs) restart_t in S.l3 (fun d t t0 -> min d (t - t0)) duration secs t0 2 React FRP engine Combinators Create primitives Updates Create primitives val E.create : unit -> 'a E.t * ('a -> unit) val S.create : 'a -> 'a S.t * ('a -> unit) Callbacks ▸ FRP let value = 60 let s_val : int S.t, set = S.create value in let s = Stepper.create ~value ~on_change:set Program structure (* create primitives *) ... (* define derived signals & events *) ... let () = while true do update_primitives () done Try it ! http://erratique.ch/software/react http://erratique.ch/talks/ocamlum-2010 OCaml & FRP Froc http://github.com/jaked/froc Concurrent cell http://ccell.forge.ocamlcore.org/ Other & FRP Haskell http://haskell.org/haskellwiki/Functional_Reactive_Programming Javascript http://flapjax-lang.org/ Scala http://lamp.epfl.ch/~imaier/ Scheme http://docs.plt-scheme.org/frtime/index.html ? Leaks Recursive values Side-effects (eq.) Runtime costs Program struct. .

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An Empirical Study on Program Comprehension with Reactive Programming
Jens Knoop, Uwe Zdun (Hrsg.): Software Engineering 2016, Lecture Notes in Informatics (LNI), Gesellschaft fur¨ Informatik, Bonn 2016 69 An Emirical Study on Program Comrehension with Reactive Programming Guido Salvaneschi, Sven Amann, Sebastian Proksch, and Mira Mezini1 Abstract: Starting from the first investigations with strictly functional languages, reactive programming has been proposed as the programming paradigm for reactive applications. The advantages of designs based on this style overdesigns based on the Observer design pattern have been studied for along time. Over the years, researchers have enriched reactive languages with more powerful abstractions, embedded these abstractions into mainstream languages –including object-oriented languages –and applied reactive programming to several domains, likeGUIs, animations, Webapplications, robotics, and sensor networks. However, an important assumption behind this line of research –that, beside other advantages, reactive programming makes awide class of otherwise cumbersome applications more comprehensible –has neverbeen evaluated. In this paper,wepresent the design and the results of the first empirical study that evaluates the effect of reactive programming on comprehensibility compared to the traditional object-oriented style with the Observer design pattern. Results confirm the conjecture that comprehensibility is enhanced by reactive programming. In the experiment, the reactive programming group significantly outperforms the other group. Keywords: Reactive Programming, Controlled
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Elmulating Javascript
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