User Guide - Part One

As I promised yesterday, today, I'll start a series of entries with a very rough first user guide for the JauVM.

Lets start with the interpreter itself.

In the proposal text there's a brief description on what Interpreter objects should look like. Lets elaborate a bit on that:

Interpreter.java

package net.sf.jauvm;

public class Interpreter implements Runnable {
    private final Runnable r;

    public Interpreter(final Runnable r) {
        this.r = r;
    }

    public Interpreter(final Continuation c) {
        this.r = new Runnable() {
            public @interpretable void run() {
                c.continueFrom();
            }
        };
    }

    public void run() {
        // interpret r.run()
    }
}

This is pretty much what I had already described, though there are some new things.

As you can see, I've “added” a second constructor that takes a Continuation which is then continued when the interpreter is run. This is handy when you wish to call a continuation you've just deserialized on a new Interpreter object.

It also serves the purpose of showing you how to write an interpretable method: just tag it with the @interpretable annotation. Here is the code for this annotation:

interpretable.java

package net.sf.jauvm;

import java.lang.annotation.*;

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface interpretable {}

The fact that an Interpreter implements Runnable facilitates the creation of an interpreter on a new thread, look:

new Thread(new Interpreter(new Runnable() {
    public @interpretable void run() {
        // ...
    }
})).start();

Tomorrow, I'll shed some light what tail-calls look like.