Call an interpreted function

[fpelliccioni]

Hello,

I have the following Javascript code that I am interpreting using your library:

callback(function(x, y) { return x < y; });

I had setup a wrapper function this way:

var callback_wrapper = function(cb) {
    // **1
};

interpreter.setProperty(scope, 'callback',    interpreter.createNativeFunction(callback_wrapper));

I want to call the function passed to callback() inside the callback_wrapper() (**1).
Is it possible?
How can I do it?

Thanks in advance,

[cpcallen]

This is a duplicate of #130. Unfortunately what you want to do is not at all straight forward.(I recall having an even more extensive discussion of the issues involved in another bug, but I can't find it at the moment.)

It is possible, but it entails writing the native function as a state machine which will be invoked multiple times:

1. The interpreter invokes the native function for the first time. It does whatever needs to be done before calling the callback, then creates a new state for the call to the callback and places it on the top of the state stack.
2. Native function returns (without removing itself from the state stack), allowing interpreter to continue with execution of callback.
3. When execution of callback is complete, interpreter will re-invoke native function. It must remember that it's already done step 1. and not do it again, but instead continue with whatever it should do next.
4. Eventually the native function returns in a way that pops itself off the state stack.

The interpreter in Code City, which was originally forked from this one, has been modified with various mechanisms to facilitate this; an example of their usage can be seen in the definition of String(), which calls user-supplied .toString and .valueOf methods, but it would be a large project to back-port these changes and the Code City interpreter is not a good general-purpose replacement for JS Interpreter.

See also #147, which is related but would not by itself solve your particular issue.

[fpelliccioni]

Thank you very much for all the information.

[semiaddict]

[moved my comment to 147#1211911798]