Course Pages
- Education Page
- Description
- Literature
- Schedule
- Assignments

Center
Master Program

Functional Reactive Programming

Afp0304

Functional reactive programming, or FRP, is a paradigm for
programming hybrid systems (i.e., systems containing a combination of
both continuous and discrete components) in a high-level, declarative
way. An implementation of this concept is [[http://www.haskell.org/yampa/][Yampa]].

---++ Papers
| *paper* | *use* |
| [[http://www.haskell.org/yale/papers/oxford02/][Arrows, Robots, and Functional Reactive Programming]] Paul Hudak, Antony Courtney, Henrik Nilsson and John Peterson, 2002 | covers most of the presentation inculding AFrob (robots) |
| [[http://www.haskell.org/yale/papers/haskellworkshop02/][Functional Reactive Programming, Continued]] Henrik Nilsson, Antony Courtney and John Peterson, 2002 | dynamic collections - read it if you want to know more of AFP. For an alternative example see next paper |
| [[http://www.apocalypse.org/pub/u/antony/pubs/hw03.pdf][The Yampa Arcade]] Antony Courtney, Henrik Nilsson and John Peterson, 2003 | describes an example application witch uses dynamic collections |

   * For more info about Arrows take a look at the page of HaskellArrows or at [[http://www.haskell.org/arrows/]]
   * If you want to see the robot examples go to the [[http://www.haskell.org/yampa/][Yampa]] page and download and compile the package. This is not easy. 
      * Best changes are with Linux and GHC5 (with profiling libraries) and <nop>GreenCard.
      * If you have HGL you don't need <nop>GreenCard (you can find a binary at http://www.haskell.org/greencard/).
      * If you don't have Profiling you need to remove the profiling option in the Makefile
      * One of the installs fails because it tries to install a file twice. To fix, open the Makefile and remove the source file from the list of sources, and run make install again.
      * If you use windows. Good luck! (I hope you have an working HGL)  

---++ Assignment
Extend rcFollowWall (defined at slide 35) so that the robot turns right when the wall makes a corner to
the right.  you can use any function shown in the papers or slides.

   * use the range finder to find the distance to the wall in front of you (slide 34)
   * define =tooClose, notTooClose :: Distance -> SF <nop>RobotInput (Event ())=
   * use 'switch' to switch behavior between follow the wall or turn (slide 15)
   * use a second 'switch' to switch from turning to following the wall again (slide 15)
   * when you are stuck, make a drawing of the signal functions
   * feel free to contact me at [[mailto:cddouma@cs.uu.nl cddouma@cs.uu.nl]]

note that instead of the two switches you can use a drSwitch but it needs more understanding.

---++ Results
| *name*                | *result* |
| 9952330               | + |
| 0019593               | [] |
| 0054445               | [] | 
| Arjan Oosting         | + |
| Joost Verhoog         | - |
| Mart Kolthof          | [] |
| Niels van der Velden  | + |
| Peter Nagel           | - |
| Robert van Herk       | - |

*Common mistake:* =mrFinalize (ddVelTR v (lim 0.2 omega))= is not a Signal Function. So you cannot pass it to =switch=.

---++ Errata
   slide&nbsp;8: type of first is: SF a b -> SF (a,c) (b,c)
   slide&nbsp;12: type of constant is: b -> SF a b
   slide&nbsp;15: replace && with &&&

-- Main.DoumaCD - 22 Sep 2003

Topic attachments
I	Attachment	Action	Size	Date	Who	Comment
pdf	frp.pdf	manage	8671.9 K	21 Oct 2003 - 07:36	DoumaCD	Presentation (PDF, big!)
ppt	frp.ppt	manage	184.0 K	21 Oct 2003 - 07:35	DoumaCD	Presentation (PowerPoint, hopefully)
sxi	frp.sxi	manage	107.4 K	21 Oct 2003 - 07:34	DoumaCD	Presentation (OpenOffice Impress)