user interface - How are events who lead to UI changes handled/modelled with functional reactive programming? -


i've looked functional reactive programming, coming imperative world fail understand how functional language might react user event , adapt data , ui reflect necessary changes.

i've taken quick @ examples elm homepage, far understand allows describe (changing) output function of (changing) input (i.e. "draw rectangle @ mouse position" automatically updated , redrawn).

however, single events trigger action? example take usual app allows edit document in window. window has "new" button (or menu item) opens window instance. how work? appreciate if explain concept behind it.

the short answer is: frp inherently not purely functional, in general reactions actual external environment imperative in character. below describe "pure" approach frp, there more efficient more "imperative" approaches based on continuations.

• frp attempt declaratively deal time.

• behaviors functions of time.

◦ behavior has specific value in each instant.

• events sets of (time, value) pairs.

◦ i.e. organised streams of actions.

• 2 problems

◦ behaviors / events defined when don’t depend on future

◦ efficiency: minimize overhead

• frp synchronous: possible set events happen @ same time, , continuous: behaviors can have details @ arbitrary time resolution.

◦ although results sampled, there’s no fixed (minimal) time step specifying behavior.

◦ asynchrony refers various ideas ask people mean.

• forcing lazy list (stream) of events wait till event arrives.

• scanning through event list since beginning of time till current time, each time evaluate behavior – wasteful wrt. time&space. producing stream of behaviors stream of time allows forget events in past.

• next optimization pair user actions sampling times. action nothing corresponds sampling time when nothing happens.

• turning behaviors , events functions of time input-output streams similar optimizing interesction of ordered lists o(m n) o(m + n) time.

• can in turn define events in terms of (optional, maybe) behaviors, happening @ points in time rather varying on intervals of time.

• looks stream processing.

i discuss frp in a lecture on zippers, adaptive programming, frp , guis ocaml-centric.


Comments

Post a Comment

Popular posts from this blog

html - How to style widget with post count different than without post count -

i have border below li elements in wordpress widget types appropriate. element inside set block gives them nice easy click full width. the problem, when choose option "show post count" when adding widget such categories or archives displays post count plain text after tag , because tag block pushes post number text line below. whether choose show post count or not show post count still gives exact same element identifyer example "widget_categories". how style post count not on next line still keep links non post count list items full width? here's example on sidebar www.bbmthemes.com/themes/modular/blog-standard/ in order solve problem need remove display:block; for ul.widgets ul a , add in it's place line-height: 33px; what going achieve have same visual effect. what going lose doing links going work on text , not on "box". the other way out of find post count coming , make changes this. example change text count i
Read more

How to remove text and logo OR add Overflow on Android ActionBar using AppCompat on API 8? -

have researched death , cannot find answer. i have actionbar using appcompat. supporting api v7 (api v8 do). actionbar works api v11. api < v11 has problem of removing icon (and feature) actionbar without supplying overflow. big picture have app logo, app title, , 3 icons squidging same actionbar on low end phone. trying make room! i happy 1 of 2 solutions. either: a method of getting overflow functionality can retrieved pull down. (preferred) method of removing icon , text actionbar below current xml api 11+: <resources> <!-- base application theme api 11+. theme replaces appbasetheme res/values/styles.xml on api 11+ devices. --> <style name="appbasetheme" parent="theme.appcompat.light.darkactionbar"> <item name="android:actionbarstyle">@style/liteactionbarstyle</item> <item name="actionbarstyle">@style/liteactionbarstyle</item> </st
Read more

javascript - storing input from prompt in array and displaying the array -

i want take the inputs user prompt, store input in array, , display it. want take 10 inputs user using for loop. have tried do-while shown below. var givennames = new array(); var pattern = /[\w\d]{1,}/ig; do{ var name = prompt("enter names. letters , digits accepted!\nentering empty field stops asking",""); if(name && name.match(pattern)){givennames.push(name);} } while(name != ""); function displaynames(){ if(givennames.length > 0){ document.getelementbyid("list").innerhtml = "<span style='color:navy;font- weight:bold;'>given names are:<\/span><br><br>" + givennames.join("<br><br>"); } else { document.getelementbyid("list").innerhtml = "<span style='color:navy;font-weight:bold;'>nothing has been given!<\/span>"; } } how replace for loop? var givennames = new array();
Read more