support for something similiar to python's isInstance

[nshaheed]

Python has this function isInstance which tells you if a value is an instance of a class, i.e.

dict = {}
if isInstance(dict, dictionary):
  # do something

it would be nice to have some sort of equivalent in chuck, specifically for the case of storing different subclasses in an array:

[new SinOsc, new SndBuf, new LiSa] @=> UGen ugens[] => dac;

// this won't work
// 220 => ugens[0].freq; 

// this works, but you need to keep track of which
// index is a sinosc
330 => (ugens[0] $ SinOsc).freq; 

// what if we had something like this?
int i;
while (true) {
    if (Type.isInstance(ugens[i], SinOsc) {
        330 => (ugens[i] $ SinOsc).freq;
    }

    (i + 1) % 3 => i;
}

eon => now;

That way, even if the type info gets lost because it needs to be cast to a more general type, we can still get back to its original type