python bytecode grammar

[Terry Reedy]

"Peter Dembinski" <pdemb at gazeta.pl> wrote in message 
news:874qc3inla.fsf at hector.domek...
> "Terry Reedy" <tjreedy at udel.edu> writes:
>> I believe the top-level production is something like
>> BYTECODE := (OPCODE ARGS)*
>
> ROTFL :)

Glad to make your day ;-)

I am aware that since ARGS depends on OPCODE, the above would lead to 
context-dependent productions for ARGS.  Upon thoroughly perusing
http://docs.python.org/lib/bytecodes.html
18.10.1 Python Byte Code Instructions

I discovered that there is at most one (non-stack) argument in the byte 
stream (contrary to the possibly plural implication of "All of the 
following opcodes expect arguments").  So the above could be written 
context-freely as
BYTECODE := (NO_ARG_CODE | ARG_CODE TWO_BYTE_ARG)*

where the symbolic expansions of NO_ARG_CODE  and ARG_CODE, with semantic 
explanations, constitute the contents of the doc above.

Terry J. Reedy