bytecode JUMP_IF_* always followed by POP_TOP?

[Michael Hudson]

"Robert Brewer" <fumanchu at amor.org> writes:

> Tim Peters wrote:
> > [Robert Brewer]
> > > Playing around with bytecodes some more:
> > > ...
> > > I notice that, whether JUMP_IF_FALSE jumps or not, the next
> > > instruction it executes is POP_TOP
> > > ...
> > > Are there any constructions whereby this does not happen for
> > > JUMP_IF_FALSE and JUMP_IF_TRUE?
> > 
> > Try
> > 
> >     x and y
> > 
> > and
> > 
> >     x or y
> > 
> > When those jump, they want to retain the tested value, so 
> > there's no POP_TOP
> > at the branch target then.
> 
> Ah. They only POP_TOP if they *don't* jump. Got it. Thanks!

I think you may want to play around with chained comparisons, too,
IIRC.  We Have Been Here Before :-)

Cheers,
mwh

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