---++ wxHaskell
In the course we will tell something about the programming of graphical user interfaces in Haskell. Unfortunately there is not a single, well-defined way to do so, since there are quite a few, more or less equally expressive, packages available. All these packages rely on haskell bindings to some external graphical user-inerface library, such as OpenGL, wxWidgets or GTK. We will use [[http://www.haskell.org/haskellwiki/WxHaskell][wxHaskell]]

Due to the fact that both the main haskell compiler GHC evolves, these packages evolve, and the operating systems on which they are to be combined evolve, getting a working combination of these three components is not always easy. The situation has improved however over the years. Especially on Widows based systems the situation has been somewhat problematic. In order to make your life easier we have constructed a zip file which contains a working combination of the wxWidgets, the [[http://www.haskell.org/haskellwiki/WxHaskell][wxHaskell]] modules, and the GHC Haskell compiler. It contains also an example application  which is based on the so-called turtle graphics, which enables you to program line drawings by giving commands to a turtle who draws lines by moving over a piece of paper. The nice thing is that you do not need a lot of haskell knowledge to start using it.

In order to use this package:
   * download the [[http://people.cs.uu.nl/ariem/turtle-graphics.zip][package]]
   * unpack the zip file
   * double-click on start.bat and type _main_ in order to run the main program
   * using a text editor to change the file  [[%ATTACHURL%/Turtle.hs][Turtle.hs]]
   * the file [[%ATTACHURL%/Turtle.pdf][Turtle.pdf]] contains an exercise (in Dutch)


<!--
De Prolog Interpretator en een file met een paar Prolog definities. 

   * [[%ATTACHURL%/PrologInHaskell.hs][PrologInHaskell.hs]]
   * [[%ATTACHURL%/voorbeeld.prl][voorbeeld.prl]]

Voorbeeld van gebruik:
<verbatim>
$ ghci PrologInHaskell.lhs 
GHCi, version 6.10.4: http://www.haskell.org/ghc/  :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer ... linking ... done.
Loading package base ... linking ... done.
[1 of 1] Compiling PrologInterpreter (PrologInHaskell.hs, interpreted )
Ok, modules loaded: PrologInterpreter.
*PrologInterpreter> main
Loading package syb ... linking ... done.
Loading package base-3.0.3.1 ... linking ... done.
Loading package array-0.2.0.0 ... linking ... done.
Loading package filepath-1.1.0.2 ... linking ... done.
Loading package old-locale-1.0.0.1 ... linking ... done.
Loading package old-time-1.0.0.2 ... linking ... done.
Loading package unix-2.3.2.0 ... linking ... done.
Loading package directory-1.0.0.3 ... linking ... done.
Loading package process-1.0.1.1 ... linking ... done.
Loading package random-1.0.0.1 ... linking ... done.
Loading package haskell98 ... linking ... done.
Loading package uu-parsinglib-2.3.0 ... linking ... done.
File with rules? voorbeeld.prl
ma(mien, juul):-.
ma(juul, bea):-.
ma(bea, alex):-.
ma(bea, cons):-.
oma(X, Z):-ma(X, Y), ouder(Y, Z).
append(nil, X, X):-.
append(cons(A, X), Y, cons(A, Z)):-append(X, Y, Z).
pa(alex, ale):-.
pa(alex, ama):-.
pa(alex, ari):-.
ma(max, ale):-.
ma(max, ama):-.
ma(max, ari):-.
ouder(X, Y):-pa(X, Y).
ouder(X, Y):-ma(X, Y).
voor(X, Y):-ouder(X, Y).
voor(X, Y):-ouder(X, Z), voor(Z, Y).
term? voor(alex,X)
goal                 : voor(alex, X)
unifies with head of : voor(X0, Y0):-ouder(X0, Y0).
new environment      : [("X0",alex),("X",Y0)]
new goals            : [ouder(X0, Y0)]

goal                 : ouder(X0, Y0)
unifies with head of : ouder(X1, Y1):-pa(X1, Y1).
new environment      : [("X1",alex),("Y0",Y1),("X0",alex),("X",Y0)]
new goals            : [pa(X1, Y1)]

goal                 : pa(X1, Y1)
unifies with head of : pa(alex, ale):-.
new environment      : [("Y1",ale),("X1",alex),("Y0",Y1),("X0",alex),("X",Y0)]
new goals            : []

X = ale
q
goal                 : voor(alex, X)
unifies with head of : voor(X0, Y0):-ouder(X0, Y0).
new environment      : [("X0",alex),("X",Y0)]
new goals            : [ouder(X0, Y0)]

goal                 : ouder(X0, Y0)
unifies with head of : ouder(X1, Y1):-pa(X1, Y1).
new environment      : [("X1",alex),("Y0",Y1),("X0",alex),("X",Y0)]
new goals            : [pa(X1, Y1)]

goal                 : pa(X1, Y1)
unifies with head of : pa(alex, ama):-.
new environment      : [("Y1",ama),("X1",alex),("Y0",Y1),("X0",alex),("X",Y0)]
new goals            : []

X = ama

goal                 : voor(alex, X)
unifies with head of : voor(X0, Y0):-ouder(X0, Y0).
new environment      : [("X0",alex),("X",Y0)]
new goals            : [ouder(X0, Y0)]

goal                 : ouder(X0, Y0)
unifies with head of : ouder(X1, Y1):-pa(X1, Y1).
new environment      : [("X1",alex),("Y0",Y1),("X0",alex),("X",Y0)]
new goals            : [pa(X1, Y1)]

goal                 : pa(X1, Y1)
unifies with head of : pa(alex, ari):-.
new environment      : [("Y1",ari),("X1",alex),("Y0",Y1),("X0",alex),("X",Y0)]
new goals            : []

X = ari

term? stop
*PrologInterpreter> :q
Leaving GHCi.
</verbatim>
-->
Topic attachments
I	Attachment	Action	Size	Date	Who	Comment
hs	Turtle.hs	manage	8.5 K	09 Sep 2010 - 07:53	DoaitseSwierstra
pdf	Turtle.pdf	manage	158.5 K	09 Sep 2010 - 07:53	DoaitseSwierstra