Extension Method?

[oldrev]

Hi all:

Recently, I have found a undocumented(?) feture that a individual function with one parameter of array can be used as a method:

int getLength(int[] arr) { return arr.length; }
int[] foo = [1, 2, 3];
int len = foo.getLength();

Where I can find the information for this?

Thanks a lot!.

regards.