[Zope-ZEO] Need for PersistentList

[Jim Fulton]

"John D. Heintz" wrote:
> 
> Jim Fulton wrote:
> 
> > Andrew Kuchling wrote:
> >
> >> On Thu, Jan 18, 2001 at 03:40:02PM -0500, Jim Fulton wrote:
> >>
> >>> I would be reluctantly willing to include something like
> >>> PersistentList in ZODB is I had some evidence that people actually
> >>> needed it. Persistent sequences seem to be like persistent mappings
> >>
> >> Really?  Their absence drove us nuts, because whenever someone mutated
> >> a list directly, it led to confusion and time lost to tracking it
> >> down, so we wrote PersistentList and now use it all over the place.
> >> Perhaps it's because we have lists of things all over the place --
> >> steps, parameters -- while there seems less use for them in Zope,
> >> where things are usually accessed by name.
> >
> >
> > Hm.  I wonder what other peoples needs have been.
> 
> I'm glad you asked. ;-)  We have definetly felt a need for
> PersistentList and soon will be migrating to Andrew's PersistentList
> impl in our code.

OK, then if Andrew is willing, I suggest we include PersistentList
in ZODB. O

> We have also had a strong need for PersistentSet data structures with
> union/intersection/...

I'm working on a newversion of BTrees that include sets (BTrees
without values).  We could provide union/intersection/subtraction
operators that work with these.

Note that we cirrently provide persistent integer sets.
 
> Finally, we need for Persistent classes to be hashable.

Are they not hashable now?

Jim

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