Re: [Jscheme-user] Handling Java Array Parameters

[Ken A. <kan...@bb...>]

You can also make an array with (array class arg ...) or
(make-array class size)  and access array elements with the Scheme primitives vector-ref and vector-set!  They work on any array type.

If you're interested in dynamic classpath hacking, see elf/classpath.scm.
It provides (url) which will create a URL from a File, String or URL.
It also provides addClasspathUrl which will extend the classpath, of the classloader that loaded JScheme, by a url.

I use this to make my JScheme environment automatically know about nearby jars.  So, for example, if you start JScheme with something like:

java -jar lib/jscheme.jar

Then the following code will find the lib/ directory, and home directory of the application, and add all the jar's in lib/ to the classpath:

(load "elf/classpath.scm")
(load "using/run.scm")

;;; lib directory.
(define libDir (.getCanonicalFile
                (.getParentFile (File. ($ "java.class.path")))))

;;; Application home directory.
(define appDir (.getParentFile libDir))

''' Extend classpath.
(for-each addClasspathUrl (files** libDir isJarFile))
At 10:58 PM 3/1/2004 -0500, Timothy John Hickey wrote:

>On Monday, March 1, 2004, at 09:59 PM, Enrique Ricoy Belloc wrote:
>
>>I've started using Jscheme, I want to implement the
>>following code, but
>>don't know quite how to handle the URL[] definition:
>>
>>
>>URL[] urls = new URL[] {
>>new File("C:\\Program Files\\Microsoft SQL Server 2000
>>Driver for
>>JDBC\\lib\\msbase.jar").toURL(),
>>new File("C:\\Program Files\\Microsoft SQL Server 2000
>>Driver for
>>JDBC\\lib\\mssqlserver.jar").toURL(),
>>new File("C:\\Program Files\\Microsoft SQL Server 2000
>>Driver for
>>JDBC\\lib\\msutil.jar").toURL()
>>};
>
>I tend to use the (list->array TYPE LIST) procedure
>which converts a list into an array of the specified type.
>So, to convert a list L of filenames into an array of URLs
>you could use the following procedure:
>
>> (define (filenames->urlarray L)
>  (list->array java.net.URL.class
>    (map .toURL
>       (map java.io.File. L))))
>......
>
>which could be applied as follows:
>
>> (define z (filenames->urlarray (list "lib/jscheme.jar" "lib/applet.jar")))
>.....
>> z
>#(file:/Users/tim/Research/Software/jscheme/lib/jscheme.jar file:/Users/tim/Research/Software/jscheme/lib/applet.jar)
>
>Hope this helps,
>---Tim---
>
>P.S. You can access array elements with (Array.get z n) and (Array.set z n v), e.g.
>
>> (Array.get z 0)
>...
>> (Array.set z 1 (Array.get z 0))
>...
>
>
>
>>URLClassLoader loader = new URLClassLoader(urls);
>>Driver d = (Driver) Class.forName(driverStr, true,
>>loader).newInstance();
>
>This would rewrite to
>(define loader (URLClassLoader. urls))
>(define d (.newInstance (Class.forName driverStr #t loader)))
>
>>
>>--end--
>>
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