From: Edward K. Ream
To: leo-editor
Sent: Friday, October 14, 2016 3:22 PM
Subject: Re: reversed iterators
On Fri, Oct 14, 2016 at 1:42 PM, 'Terry Brown' via leo-editor
wrote:
Something that just struck me. I want to add, to all the nodes on a
multi-level subtree, two child nodes. Here's the code I used:
for nd in reversed([i for i in p.subtree_iter()]): nd.insertAsLastChild().h
= 'src' nd.insertAsLastChild().h = 'clip'c.redraw()
I don't think that would have worked without the reversed(), maybe because
positions would get corrupted (maybe not, after the recent addition of .copy()
on iterator yields?), but definitely because it would end up recursively adding
the pair of child nodes to themselves.
Careful, the theory of operations for c.deletePositionsInList explains why
there is no order for deleting a set of nodes. See Code-->Core classes-->@file
leoCommands.py-->class Commands-->c.deletePositionsInList--><< theory of
operation >> (deletePositionsInList)
Hmm, good point, I was only thinking of insertions. And of course, "Clones
Spoil Everything"(TM), so I'm sure there are traps there too. Still, for my
use case, reversed() certainly seems like the simplest way, otherwise you'd
need to collect gnxs or something.
Cheers -Terry
It's hard to remember the argument, but the conclusion is engraved in my bean:
"the conclusion...is we must use the positions passed to
p.deletePositionsInList only as *hints* about what to do."
Reversed iterators may be safe in some situations, but usually they are just as
unsafe as forward iterators. So it seems that providing reversed iterators is
going to give people a false sense of security.
Edward
--
You received this message because you are subscribed to the Google Groups
"leo-editor" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to leo-editor+unsubscr...@googlegroups.com.
To post to this group, send email to leo-editor@googlegroups.com.
Visit this group at https://groups.google.com/group/leo-editor.
For more options, visit https://groups.google.com/d/optout.
--
You received this message because you are subscribed to the Google Groups
"leo-editor" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to leo-editor+unsubscr...@googlegroups.com.
To post to this group, send email to leo-editor@googlegroups.com.
Visit this group at https://groups.google.com/group/leo-editor.
For more options, visit https://groups.google.com/d/optout.
