Re: HAMT iterator

[Marc Nieper-Wißkirchen]

Am So., 11. Okt. 2020 um 14:14 Uhr schrieb Bruno Haible <bruno@clisp.org>:

[...]

> > > > /* Return an independent copy of ITER that is initially in the same
> > > >    state.  */
> > > > extern Hamt_iterator *hamt_iterator_copy (Hamt_iterator *iter);
> > >
> > > Then a copy function is not needed, because the user's program can do
> > >
> > >   Hamt_iterator iter_clone = iter;
> >
> > The hamt itself has to be copied (to increase the reference counter).
>
> Whether copying an iterator can be done by assignment or requires a function
> call, is of second importance.
>
> The more important point I wanted to make: Does allocating an iterator
> require a (heap) memory allocation?
>
> If you iterate with do_while, no memory allocation is needed, because all
> information is stored on the stack, between the various function calls.
>
> If you iterate with hamt_iterator_create, and the Hamt_iterator type
> has bounded size (I guess it will not require more than 15 pointers and
> 13 indices), it can be stored on the caller's stack.

That's a very good point you make. The hamt iterator has, of course,
(low) bounded size, so it can (and should) be allocated on the stack.