On 5/22/2013 9:30 AM, Edward K. Ream wrote:
Here is the first draft of a tutorial for positions. It wasn't easy.
All comments welcome.
A **position** object represents a specific node in a Leo outline.
Equivalently, a position represents the state of a Leo generator, that is,
a specific node during a traversal of a Leo outline.
Because of clones, a node may appear arbitrarily many times in an outline,
so a node may appear at arbitrarily many positions in the outline.
For any position p, **p.v** is the vnode at position p.
A node's vnode never changes, regardless of where the node appears in the
outline, and regardless of whether the node is cloned or not.
**Positions become invalid when the outline changes.**
You may save and and use positions *provided* the outline remains
unchanged.
Leo's generators deliver positions, one after each other, using a *single*
(ever-changing) position. As a result, scripts must use p.copy() to create
lists of positions. For example,
aList = [p.copy() for p in c.rootPosition().subtree()]
Edward
P.S. I considered using an example outline containing clones,
but I'm not sure that adds enough to be worth including in a precis.
EKR
That last bit about p.copy() just enlightened me all over the place...
This is a good draft. I like it as is.
-->Jake
--
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 [email protected].
To post to this group, send email to [email protected].
Visit this group at http://groups.google.com/group/leo-editor?hl=en-US.
For more options, visit https://groups.google.com/groups/opt_out.
