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Functional Reactive Programming

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(From [http://www.haskell.org/frp/ www.haskell.org/frp/], last updated 2003)
(Introduction: Netwire 4 is now on HackageDB.)
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Functional Reactive Programming integrates time flow and compositional events into functional programming. This provides an elegant way to express computation in domains such as interactive animations, robotics, computer vision, user interfaces, and simulation.
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Functional Reactive Programming (FRP) integrates time flow and compositional events into functional programming. This provides an elegant way to express computation in domains such as interactive animations, robotics, computer vision, user interfaces, and simulation.
   
The following libraries are implementations of FRP:
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  +
== Introduction ==
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FRP is about domain-specific languages that capture the notion of
  +
time-varying values. Let's take Netwire 4 as an example. You can install it either from HackageDB,
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  +
cabal install netwire
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  +
or by grabbing the latest source code via darcs:
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  +
darcs get http://darcs.ertes.de/netwire/
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cd netwire
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cabal install
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  +
Imagine you have a simple GUI label that displays the number of seconds
  +
passed since program start. In an event-based model this is actually
  +
quite a complicated task. You would have to create a label and update
  +
it all the time using some form of timer/idle event. In Netwire you
  +
write:
  +
  +
myLabel = time
  +
  +
Now let's say you want to have the same GUI, but the time should start
  +
at 10 and pass twice as fast, so you actually want to display twice the
  +
number of seconds passed plus 10:
  +
  +
myLabel = 10 + 2*time
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  +
Imagine you want to display the string "yes" in a label:
  +
  +
myLabel = "yes"
  +
  +
Now let's say you want to display "yes", when the space key is held down
  +
and "no" otherwise:
  +
  +
myLabel = "yes" . keyDown Space <|> "no"
  +
  +
You want to display time while pressed and "Press space" while not:
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myLabel = fmap show time . keyDown Space <|> "Press space"
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  +
You want to display "yes" every other second and "no" otherwise:
  +
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myLabel = "yes" . holdFor 1 (periodically 2) <|> "no"
  +
  +
Imagine doing that with event-based code.
  +
  +
Summary: FRP is about handling time-varying values like they were
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regular values.
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== Libraries ==
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* [http://hackage.haskell.org/package/sodium Sodium]
 
* [[Grapefruit]]
 
* [[Grapefruit]]
 
* [[Reactive]]
 
* [[Reactive]]
 
* [[DataDriven]]
 
* [[DataDriven]]
 
* [[Yampa]]
 
* [[Yampa]]
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* [[WxFruit|wxFruit]]
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* [http://hackage.haskell.org/package/elerea Elerea]
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* [[Reactive-banana|reactive-banana]]
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* [[Netwire]]
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* [http://conal.net/fran/ Fran] (discontinued)
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* [http://hackage.haskell.org/packages/archive/pkg-list.html#cat:frp Hackage packages in the category FRP]
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  +
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== Publications and talks ==
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* [http://www.cs.rit.edu/~eca7215/frp-independent-study/Survey.pdf A Survey of Functional Reactive Programming]
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* [http://conal.net/papers/frp.html Conal Elliott’s FRP-related publications]
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* [https://grapefruit-project.org/publications-and-talks Grapefruit-related publications and talks]
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* [http://haskell.cs.yale.edu/?page_id=65#FunctionalReactiveProgramming The Yale Haskell Group’s FRP-related publications]
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== From [http://www.haskell.org/frp/ www.haskell.org/frp/], last updated 2003 ==
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== Blog posts ==
This is a copy of the obsolete /frp/, added so a link from http://en.wikipedia.org/wiki/Functional_reactive_programming could be losslessly repointed from there to here.
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* [http://apfelmus.nfshost.com/blog.html#functional-reactive-programming-frp FRP-related posts on Heinrich Apfelmus’ blog]
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* [http://conal.net/blog/tag/frp FRP-related posts on Conal Elliott’s blog]
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* [http://jeltsch.wordpress.com/tag/frp/ FRP-related posts on Wolfgang Jeltsch’s blog]
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* [http://lukepalmer.wordpress.com/2008/11/28/relative-time-frp/ Relative time FRP] by Luke Palmer
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* [http://blog.edwardamsden.com/2011/03/demonstrating-time-leak-in-arrowized.html Demonstrating a Time Leak in Arrowized FRP] by Edward Amsden
   
*[http://www.haskell.org/yale/publications.html The Yale Haskell group's latest publications] - Most are related to FRP
 
*[http://conal.net/papers Conal Elliott's papers] - Several are on FRP
 
*[http://conal.net/fran Fran] - Functional Animation
 
   
People:
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== People ==
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* [http://apfelmus.nfshost.com/ Heinrich Apfelmus]
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* [http://www.facebook.com/antony.courtney Antony Courtney]
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* [http://conal.net/ Conal Elliott]
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* [http://sgate.emt.bme.hu/patai/ Patai Gergely]
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* [http://www.ittc.ku.edu/csdl/fpg/Users/AndyGill Andy Gill]
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* Liwen Huang
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* Paul Hudak
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* [https://wolfgang.jeltsch.info/ Wolfgang Jeltsch]
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* [http://www.cs.nott.ac.uk/~nhn/ Henrik Nilsson]
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* [http://mcis.western.edu/~jpeterson/ John Peterson]
   
*[http://www.apocalypse.org/pub/u/antony/home.htm Antony Courtney]
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[[Category:FRP|*]]
*[http://conal.net Conal Elliott]
 
*[http://pantheon.yale.edu/~lh234/ Liwen Huang]''broken link''
 
*[http://www.cs.yale.edu/homes/hudak-paul.html Paul Hudak]''broken link''
 
*[http://www.cs.yale.edu/~nilsson Henrik Nilsson]
 
*[http://mcis.western.edu/~jpeterson/ John Peterson]
 

Revision as of 16:24, 16 November 2012

Functional Reactive Programming (FRP) integrates time flow and compositional events into functional programming. This provides an elegant way to express computation in domains such as interactive animations, robotics, computer vision, user interfaces, and simulation.


Contents

1 Introduction

FRP is about domain-specific languages that capture the notion of time-varying values. Let's take Netwire 4 as an example. You can install it either from HackageDB,

   cabal install netwire

or by grabbing the latest source code via darcs:

   darcs get http://darcs.ertes.de/netwire/
   cd netwire
   cabal install

Imagine you have a simple GUI label that displays the number of seconds passed since program start. In an event-based model this is actually quite a complicated task. You would have to create a label and update it all the time using some form of timer/idle event. In Netwire you write:

   myLabel = time

Now let's say you want to have the same GUI, but the time should start at 10 and pass twice as fast, so you actually want to display twice the number of seconds passed plus 10:

   myLabel = 10 + 2*time

Imagine you want to display the string "yes" in a label:

   myLabel = "yes"

Now let's say you want to display "yes", when the space key is held down and "no" otherwise:

   myLabel = "yes" . keyDown Space <|> "no"

You want to display time while pressed and "Press space" while not:

   myLabel = fmap show time . keyDown Space <|> "Press space"

You want to display "yes" every other second and "no" otherwise:

   myLabel = "yes" . holdFor 1 (periodically 2) <|> "no"

Imagine doing that with event-based code.

Summary: FRP is about handling time-varying values like they were regular values.

2 Libraries


3 Publications and talks


4 Blog posts


5 People