[Jscheme-devel] Re: [Jscheme-user] javacdoc for jscheme

[Timothy H. <tim...@ma...>]

On Tuesday, June 18, 2002, at 10:03 AM, tleek wrote:

>
> Hi,
>
> I'm using JScheme from java but having some difficulties.  Is there
> javadoc out there?

I've created a javadoc for jscheme:
      http://www.cs.brandeis.edu/~tim/jscheme/doc/javadoc/

>  I don't even know, e.g., if
>
> foo = JS.eval(schemeCommand);
>
> throw an exception that needs catching.

Jscheme wraps all of its exceptions as subclasses of RuntimeException
so you are not forced to catch them.

It is a good idea to have the Scheme code catch the exception:
  try
     foo= JS.eval("(tryCatch ..SchemeCode.. (lambda(e) e))");
  catch(Exception e) { .... };

If the exception is thrown inside SchemeCode during a reflection call to 
Java,
then the tryCatch will

For example, here is a test program which wraps Scheme expressions in
a tryCatch:

> import jscheme.JS;
>
> public class Test {
>     public static void main (String[] args) {
>         Object foo = JS.eval("(tryCatch "+ args[0] + "(lambda(e) e))");
>         System.out.println("foo= "+foo);
>         System.out.println("foo class is "+foo.getClass());
>     }
> }
>

and here are some examples of its use:

> % java -cp lib/jscheme.jar:. Test "(java.io.Socket. {129.64.3.193} 
> 14232)"
> Javadot WARNING: Can't find classjava.io.Socket
> foo= SchemeException:[[ERROR: undefined variable "java.io.Socket."]]
> foo class is class jscheme.SchemeException
>

A Scheme error (e.g. making a mistake in the javadot notation, will 
return as
a SchemeException object. This kind of error can be caught during 
debugging
hopefully.


> % java -cp lib/jscheme.jar:. Test "(java.net.Socket. {129.64.3.193} 
> 14232)"
> foo= java.net.ConnectException: Connection refused
> foo class is class java.net.ConnectException

Otherwise, if the error is thrown by a Java method or constructor, then 
the
error itself will be returned and one can test for the type of error. 
Here we tried
to open a Socket unsuccessfully.

>
>
> % java -cp lib/jscheme.jar:. Test "(/ 1 0)"
> foo= java.lang.ArithmeticException: / by zero
> foo class is class java.lang.ArithmeticException
>

Here we divide by zero and get an ArithmeticException


>
> Help!

Does this help?

>
> p.s. Can you respond to this email address with any assistance.  I'm not
> on these lists.
>
> --
>
> ================================================
>                 Tim Leek, S1-480
>                 BMD Systems and Analysis
>
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>    (_)/ (_)     Lexington, MA 02420-9108
>
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>
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>                 http://rezrov   (Lab internal)
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