Hi Thomas,
Some quick answers in addition to Nigel's
> 1) tail recursion
We use the usual "trampoline" trick, with a little top-level interpretative
loop. Using the trick has a pleasant side effect that we can pass values on
the arguments stack as well.
> 2) polymorphism
All type informations gets erased, ie polymorphism in the source language
becomes "Object" in Java.
> 3) closures & eval (i.e., laziness)
Below is the example code generated for S f g x = f x (g x). Thunk objects
intercept evaluation and update their code field. You recognize the
trampoline-trick as we return f instead of ENTER-ing it.
public class S implements Code {
public Object ENTER () {
VM.COLLECT(3, this);
final Object f = VM.POP();
final Object g = VM.POP();
final Object a = VM.POP();
VM.PUSH(new Thunk(new Code(){
public Object ENTER () {
VM.PUSH(a);
return g;
}
}));
VM.PUSH(a);
return f;
}
}
You will find a little more detail on
<http://www.cs.uu.nl/~erik/MondrianDescription.html> and on the Mondrian
homepage <http://www.mondrian-script.org/>.
We are trying to come with a new release real soon,
Erik
