Re: data type that preserve order

[Marcus Karlsson <mk acc umu se>]

On Sat, Oct 31, 2015 at 07:10:20AM +0000, Andrea Zagli wrote:
> Il giorno ven 30 ott 2015 19:09:47 CET, Emmanuele Bassi ha scritto:
> > Hi;
> >
> > On 30 October 2015 at 16:43, Andrea Zagli <azagli libero it> wrote:
> > > is there a data type, similar to array, that preserve the order on which
> > > elements are inserted?
> >
> > All the array and list types preserve the order of insertion. For
> > obvious reasons, GHashTable doesn't.
> >
> > > for example ghashtable and gptrarray doesn't preserve the order, so when
> > > they are traversed (for example with a "for" cicle, regarding gptrarray) the
> > > order may be not the same when elements are inserted
> >
> > GPtrArray preserves the order of insertion — it's an array, after all.
> > Why do you think it does not?
>
> it is written on the help
>
> https://developer.gnome.org/glib/stable/glib-Pointer-Arrays.html
>
> "If you remove elements from the array, elements at the end of the
> array are moved into the space previously occupied by the removed
> element. This means that you should not rely on the index of
> particular elements remaining the same."
>
>
> may be also other data type makes the same thing? i didn't find
> reference about that

It depends on how elements are removed from the array, there are two
ways to do it. If you use g_ptr_array_remove then the following elements
are moved down once place and the order is preserved. However if you
instead use g_ptr_array_remove_fast then the last element is moved to
fill the void. GArray offers the same two methods as well.

                Marcus