[Gambas-user] RFC: How to identify vertices and edges in a Graph class?

[Tobias Boege]

On Mon, 07 Jul 2014, Beno?t Minisini wrote:
> Le 07/07/2014 10:51, Tobias Boege a ?crit :
> >
> > We keep these generalisations and advanced topics in mind but for now, one
> > point I can and want readily apply is: in your opinion, it would be better
> > to address vertices by Strings, in a human-readable form, not just integers,
> > right? I'm still torn.
> >
> > I will make the Graph act like a Collection, i.e. once you have associated a
> > value to an ID, that ID is not changed by other operations on the Graph. You
> > had a point there; everything else hardly bearable for the programmer.
> > However, I want to use Integers as IDs because they are easier to store and
> > sort and abstract enough for the job.
> >
> > If you want to associate more human-readable names with your vertices, I
> > think you can easily achieve it by having a Collection asscoaite your names
> > with the numerical IDs. In fact that's what I'd do in the Graph internals if
> > I was to offer String IDs.
> >
> > Regards,
> > Tobi
> >
> 
> Internally, you have to use an hash table anyway, haven't you? You just 
> don't want to necessarily use string keys, as they are heavier than 
> integer keys?
> 

Oh! My thoughts were: I'll need a translation table for vertex IDs into
internal indices (e.g. over an adjacency matrix) and to search for a
mapping, that table must be sorted, so I have to compare a lot. That alone
would actually be negligible overhead. And with a hash table, not even
this problem arises. Thanks for doubting me :-) No problem to use String
keys straight from the beginning.

> Anyway, you must use a Collection-like interface to access the graph 
> nodes (to be consistent with the other Gambas containers). You can use 
> integer keys with no problems, as later you can switch to string keys 
> and keep the backward-compatibility.
> 
> You can have both too : I mean having a Gambas hash table to reference 
> nodes by names, and a special hash table using integer keys. A void hash 
> table does not take a lot of memory.
> 

How would I write the signature of _get() down in this case?

Regards,
Tobi

-- 
"There's an old saying: Don't change anything... ever!" -- Mr. Monk