dave wrote:
I was dimly aware of the functioning of booleans, but I see now that it
doesn't specify an actual boolean type. Still, the code confuses me. Is the
usage of pad_for_usrp consistent with it being treated as a boolean? Why
would the entire self reference be transmitted then?
Parameter passing in Python is fast -- the object (which may be large)
is not copied unless you explicitly make a copy. So it is no faster to
pass a big, complex object than a lightweight object like True or False.
(Implementation note: in CPython, the main Python implementation which
you almost certainly are using, objects live in the heap and are passed
around as pointers.)
The code you show isn't very illuminating as far as pad_for_usrp goes.
All that happens is that it gets stored as an attribute, then later gets
passed on again to another function or class:
class ieee802_15_4_mod_pkts(gr.hier_block2):
...
self.pad_for_usrp = pad_for_usrp
def send_pkt(self, seqNr, addressInfo, payload='', eof=False):
...
pkt = make_ieee802_15_4_packet(FCF,
seqNr,
addressInfo,
payload,
self.pad_for_usrp)
So it's *consistent* with being used as a bool, or anything else for
that matter! I expect that make_ieee802_15_4_packet may be the thing
that actually does something useful with pad_for_usrp.
Another thing to look for is the transmit_path class itself. If it has a
__len__, __bool__ or __nonzero__ method, then it has customized the way
it appears as a boolean. If it has none of those methods, then it will
always be considered true-valued, and I can't imagine why it is being
used as pad_for_usrp instead of just passing True.
But without looking at the rest of the code, I can't really tell for sure.
--
Steven
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