Re: [Boost-users] How to find edge between two vertices of undirected graph?

Subject: Re: [Boost-users] How to find edge between two vertices of undirected graph?
From: Jeremiah Willcock (jewillco_at_[hidden])
Date: 2010-06-14 11:41:01

On Sun, 13 Jun 2010, Eric Fowler wrote:

> 
> 
> On Fri, Jun 11, 2010 at 12:29 PM, Jeremiah Willcock <jewillco_at_[hidden]> wrote:
>       On Thu, 10 Jun 2010, Eric Fowler wrote:
>
>             It seems I do not have a mutable graph. This sort of raises another issue: how do I declare an object that is described by a concept? 
> 
> 
> The best you can do is apply a concept checking class.  That doesn't filter the members so you can only use the MutableGraph-required functions, but it at least makes
> sure that the graph you have is a MutableGraph.
>
>       For example, in this case I know I need a MutableGraph, and I see from the doc (http://www.boost.org/doc/libs/1_43_0/libs/graph/doc/MutableGraph.html) that
>       MutableGraphs
>       have certain properties, such as DefaultConstructible, etc. 
>
>       Now, how do I declare a MutableGraph, and know I have one? I know that:
>
>        typedef adjacency_list<vecS, vecS, undirectedS, POS<position_type> LEN<position_type> > DG;
> 
> 
> What methods are missing?  Could you please try applying the MutableGraph concept checking class to the DG type and see what breaks?
> 
> 
> Again I must ask: How? I have mined the examples and come up with: 
> BOOST_CONCEPT_ASSERT((MutableGraph<DG>));
> and 
> BOOST_CONCEPT_ASSERT((MutableGraph<DG<int>)); 
> BOOST_CONCEPT_ASSERT((BidirectionalGraph<DG<int>)); 
> 
> and put them the head of a .cpp file that uses DG. These have generated obscure and unhelpful error messages. 

The first line is the one that's correct; what errors does that produce? 
The other two CONCEPT_ASSERT lines you put are not syntactically correct.

> Copying this line from the examples and using it in the same place produces no errors: 
> 
> BOOST_CONCEPT_ASSERT((BidirectionalIterator<std::list<int>::iterator>));
> 
> 
> 
> What do you mean?  You want to add methods/functions to the graph type to make it model a specific concept?
> 
> 
> No. I mean, yes. I want to know how to define my graph type so it models a specific concept. 

You'd need to look at the documentation and then write the appropriate 
functions.  Beyond that, the concept checking classes are currently the 
only compiler-based help you get without actual concepts in C++.

-- Jeremiah Willcock