[Gambas-user] Data Structures like C++

[Bruce]

On Mon, 2012-05-21 at 22:25 +0200, Benoît Minisini wrote:

> * Tree
> * Graph
> 
> Native implementation of that would be interesting.
> 
> Any volunteer? :-)
> 
I think trees are easily implemented directly in gambas using Emil's
suggestions regarding object references as a general n-tree can be
implemented as a B-tree using something like
 
    Class CNode
        public data as Variant
        public left as CNode
        public right as CNode
    Public Sub PreOrder() as Variant[]
        blah blah ... etc  according to Mr Knuth
    End

where "left" is the first child and "right" is the first sibling.  Read
Knuth Vol 3 for the truth (I had to go searching through the attic to
find my copy.)

        Now Graphs are   M U C H   more interesting!  
        
        Someone said that they couldn't think of a use for them.  Well
        here's one, UML diagrams are all directed graphs. In fact much
        of OO thinking is actually (mathematically) directed graphs.
        Nodes and edges. From use cases through structural models,
        component models, in fact the whole she-bang.


Getting back to trees. The funny thing is that I had a real need to
construct a n-tree this week to solve a problem I had with populating a
gambas treeview from a persistence store where the nodes where out of
order, i.e. the parents were later in the storage than the children (the
code is a hack and I choose not to share it.)  Suffice to say that
Demosthenes original post prompted me to go searching through the attic.

.. found some interesting stuff, by the way .. (No, lets not go there.)

Getting back to the point, I think a gb.datastructures component is an
excellent idea.  I can't help much on the dev side as I'm pretty poor at
C/C++ (can "read only") and am totally lost with Benoit's macros but I'd
be willing to put in much effort at testing and proving. Ah! Linked
lists, how many times have I needed them and built them from scratch.

Bruce