RE: Compiling procedures questions

["Crystal, Mayer" <mayer dot crystal at gs dot com>]

Just for clarification, I've created a simple test which illustrates the
issue I am having.  The following three classes have been defined:

=====================================================================
////////////////////////////////////////////////////////
// RandomKawaProc.java
////////////////////////////////////////////////////////

import gnu.mapping.Procedure0;

import java.util.Random;

public class RandomKawaProc extends Procedure0 {
    private Random random = new Random();

    public RandomKawaProc( String name )  {
        super( name );
    }

    public Object apply0() throws Throwable {
        if ( random.nextDouble() > 0.5 )  {
            return Boolean.TRUE;
        }

        return Boolean.FALSE;
    }
}
======================================================================


======================================================================
////////////////////////////////////////////////////////
// KawaTestProcs.java
////////////////////////////////////////////////////////

public class KawaTestProcs {
    public static final RandomKawaProc testProc1 = new RandomKawaProc(
"proc1?" );
    public static final RandomKawaProc testProc2 = new RandomKawaProc(
"proc2?" );
    public static final RandomKawaProc testProc3 = new RandomKawaProc(
"proc3?" );
}
======================================================================


======================================================================
////////////////////////////////////////////////////////
// KawaTest.java
////////////////////////////////////////////////////////

import gnu.mapping.Procedure;
import kawa.standard.Scheme;

public class KawaTest {
    private static final String TEST_RULE = "(or proc1? (or proc2?
proc3?))";

    public static void main( String[] args )  {
        try  {
            Procedure proc = compileRule( TEST_RULE );
            System.out.println( "Procedure value = " + proc.apply0() );
        }
        catch( Throwable t )  {
            t.printStackTrace();
            System.exit( 1 );
        }

        System.exit( 0 );
    }

    /**
     * A helper method to compile a String rule into a Procedure.
     *
     * @param rule The string representation of the rule
     */
    private static final Procedure compileRule( String rule ) throws
Throwable {
        Scheme scheme = new Scheme( Scheme.builtin() );
        scheme.eval( "(require <" + KawaTestProcs.class.getName() + ">)" );
        String body = "( define (rule) " + rule + ")";
        scheme.eval( body );
        return (Procedure)scheme.eval( "rule" );
    }
}
======================================================================


When I run the main of KawaTest the output of the println statement is:  

	Procedure value = #<procedure proc1?>

What I was trying to do though was to get the result as true or false.


Thanks,
Mayer


-----Original Message-----
From: Per Bothner [mailto:per@bothner.com] 
Sent: Tuesday, September 28, 2004 1:51 AM
To: Crystal, Mayer
Cc: 'kawa@sources.redhat.com'
Subject: Re: Compiling procedures questions


Crystal, Mayer wrote:

> In other words, my code looks something like:
> 
> 1.  String rule =  "(or proc1? (or proc2? proc3?))";

I'd recommend wrapping the rule in a function.
Scheme doesn't have the concept of evaluating a module -
e.g. "load" returns an undefined result.  Yes, there are
ways in Kawa, but they're a bit more tricky, as the default behavior is to
ignore the values of top-level expressions.

String body = "(define (rule) (or ...))";

> 2.  Procedure moduleBody = compileRule( rule );
> 3.  return ((Boolean)moduleBody.apply0()).booleanValue();

;; Get the "rule" function in the Scheme global environment: Procedure rule
= scheme.eval("rule");

(Boolean) rule.apply0()
-- 
	--Per Bothner
per@bothner.com   http://per.bothner.com/