Re: Simple Components (Generic_Directed_Graph)

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On 2017-10-30 19:30, Victor Porton wrote:

> Oh, I've finally realized that Node_Type and Node are not the same type. Now
> your logic seems clear.
> 
> But how to solve my particular problem?
> 
> I have two objects (URI1 and URI2) of URI_Type type each (or for simplicity
> both could be two strings). I need to check if there exists a path from URI1
> to URI2. How to do this?

    URI1 : Node := new String'("http://foo.html");
    URI2 : Node := new String'("http://bar.html");
    URI3 : Node := new String'("http://baz.html");
begin
    Connect (URI1, URI2);
    Connect (URI2, URI3);
    --
    -- The graph is now:
    --
    -- "http://foo.html" -> "http://bar.html" -> "http://baz.html"
    --
    if Is_Ancestor (URI1, URI2) then
       -- There is a path in the graph

> My current idea is to use Ada standard "map" container which could map from
> "access URI_Type" to "URI_Type" (for all URIs in the considered finite set)
> before asking your generic package for existence of a path.

If you are concerned about performance in the case when same tests 
frequently repeat, you can keep a map (Node,Node)-> Boolean in order to 
cache once evaluated results.

> The same problem appears when I insert new edges: An edge should be
> identified by two values of type URI_Type but you require two accesses to
> URI_Type instead. Should I convert URI_Type to "access URI_Type" using a
> standard map before inserting into the graph?

You cannot convert it, node objects are allocated in a special storage 
pool backed by the pool passed as the package parameter. The graph 
structure is stored in that pool as well.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de