suggestion: Name predicate instructions to indicate boolean return value

[Vaguery]

I am noticing instructions like _exec_empty cropping up quite a lot. I realize that in Python variable names can only include underscores and Alnum characters, but I wonder if it might make Push code a bit more readable to name these in the Mathematica style: ending in Q (indicating "question", I guess?).

So for example _exec_empty_Q.

Just a minor suggestion. In Clojure implementations I use exec-empty?, and it helps readability quite a bit.

[erp12]

I like this idea. It will help distinguish between instruction like _exec_emtpy and _exec_flush. To someone who doesn't have a full knowledge of the instruction set, those might appear to do the same thing with the current naming.