[Boost-users] accessing internal graph properties via vertex-iterators directly?

From: Sebastian Weber (sebastian.weber_at_[hidden])
Date: 2004-11-29 09:17:13

Hello there!

First of all thanks a lot for the rapid response of my last question. I 
got another question concerning the access of internal graph properties: 
To access a bundeled vertice internal properties of a graph one has to 
use the following syntax:

struct VertStruct {
   int stuff;
};

typedef adjacency_list<vecS, vecS, undirectedS, VertStruct> graph_t;

graph_t bg;

... setup graph ...

graph_traits<graph_t>::vertex_iterator vi, vend;
tie(vi, vend) = vertices(bg);

bg[*vi].stuff = 4;

This makes it clear, that even though we already have an iterator (vi) 
pointing to our vertice of interest, the BGL has to spend again some 
time locating the data ascociated with it. A far more direct and much 
clearer notion would be:

(*vi).stuff = 4;

With this, one would save a lookup in the data-structures and the 
vertice-iterator concept would be far more logic to me, concernig 
internal property handling.

I don't know the BGL internals and how this behaviour is optimally 
programmed with the BGL. I thought of providing a custom container for 
the vertex-container which is composed of a vector of a customary 
struct, which glues vertice properties together with every element of 
the vertice list and makes the property really internal, allowing a

(*vi).myrealinternalstuff = 4

expression. I hope my point is clear.

Thanks a lot for any help.

Greetings,

Sebastian Weber