sim.app.scheme.README Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of mason Show documentation

MASON is a fast discrete-event multiagent simulation library core in Java, designed to be the foundation for large custom-purpose Java simulations, and also to provide more than enough functionality for many lightweight simulation needs. MASON contains both a model library and an optional suite of visualization tools in 2D and 3D.

The newest version!

These are Kawa/Scheme implementations of the Tutorial1 and Tutorial2 MASON
applications.  To run them:

1. Download and install, and add to your CLASSPATH the very latest 
   Kawa (at least 1.9.0) from its CVS repository
	http://www.gnu.org/software/kawa/Getting-Kawa.html
2. Run as
	java kawa.repl run1.scm		(tutorial 1)
   or
	java kawa.repl run2.scm		(tutorial 2)

Scheme is a dialect from the Lisp family of languages, and is designed to be
very small and elegant.  Kawa is a Scheme compiler and interpreter which runs
on the Java virtual machine and has nice hooks into Java proper.

What's the point?  I wanted to see how easy it was for MASON to be hooked up
with non-Java languages.  I'm an AI guy, so Lisp was the obvious choice.  :-)
Other possible language targets in the future: JRuby, Jython.  I've already
done it in BeanShell, but it was unacceptably, ridiculously slow.

Speed.  Scheme is an untyped language.  In standard Scheme form, the examples
in this directory run at 1/40 the speed of Java.  But Kawa has certain
language extensions in the form of type declarations and Java method call
forms.  Including the optional type declarations everywhere allows Kawa to
run these tutorials at about 2/3 the speed of Java!  That's VERY IMPRESSIVE
for a language which has to interface with another one to do its job.

Kawa has an extensive manual:
	http://www.gnu.org/software/kawa/toc.html
...including discussion of its (nonstandard) typing system
	http://www.gnu.org/software/kawa/Types.html
...and its (obviously nonstandard) object interface to Java
	http://www.gnu.org/software/kawa/Objects-Classes-and-Modules.html

However if you're an experienced Lisper or schemer, I've listed below just
enough for you to know to understand the code.  Enjoy.  Note that this code
is written in a Scheme fashion that very strongly resembles the Java versions
of the code.  That was intentional, as it was the easiest way to port for
proof of concept purposes.

Sean



CASE SENSITIVITY

Kawa is by default case-sensitive, which makes it a bit easier to interoperate
with Java symbols.

TYPE DECLARATIONS

Kawa makes use of type declarations in order to give compiler hints as to the
type of a variable, and also in order to access various Java classes.  A type
declaration looks like this:

				void type
				basic data types (typically java ones)
		Scheme classes
		Java classes
			Java arrays

You can type a variable using the :: operator.  This gives a hint to Kawa that
the variable will *only* hold an object of that type, which enables it to
compile to much faster code.  Without ::, the tutorial1 example runs at 1/40
the speed of the MASON Java version.  With ::, the tutorial1 example runs at
about 3/4 the speed.  Pretty impressive!

Variables are typed in various places:

	(let (x :: 
	     ((y ::  4 ))) ....

	(do ((x ::  0 (+ x 1))) ...

etc.  Basically anywhere where you define a variable or slot, you can instead 
define that variable :: .

ALLOCATING A JAVA OBJECT

(make  initialSeed)
or
( initialSeed)
; new java.util.Random(initialSeed)


CASTING INTO SUBCLASSES

(as  myButton)
; ((javax.swing.JCheckBox)myButton)


CALLING A STATIC METHOD

(:valueOf myObject)
; java.lang.String.valueOf(myObject)


CALLING SUPER

(invoke-special  (this) 'theMethodName ...args...)

CALLING AN INSTANCE METHOD ON A JAVA OBJECT

(myButton:setSize 100 200)
; myButton.setSize(100, 200)
(*:toString "Tutorial2: Life")
; "Tutorial2: Life".toString()  ;; necessary because Scheme Strings != Java Strings


GETTING/SETTING AN INSTANCE VARIABLE

myButton:val
(set! myButton:val 42)
; myButton.val    myButton.val = 42


CREATING A JAVA ARRAY WITH PREDEFINED VALUES
( 1 2 3 4)
; new int[] { 1, 2, 3, 4}
( ( 1 2) ( 3 4))
; new int[][] {{1, 2}, {3, 4}}


CREATING A JAVA CLASS WITH SCHEME METHODS AND SLOTS
(define-simple-class  ()
	-- slot --
	-- slot -- ...)

where -- slot -- can be a constructor, a method, or an instance variable.

Constructor  (args can be typed):

((*init* ...args...) ... :: ... ...body...)

Method    (args can be typed):

((methodName ...args...) ... ::  ... ..body...)

Instance variable:

(variablename
	...optional type: ...
	...optional init-form: initial-value-expression... )


ACCESSING THIS

(this)


TESTING FOR JAVA NULL

(eq? thing-to-compare #!null)