Re: [Boost-Users] [BGL] undirectedS self-loop add_edge assertion

From: Jeremy Siek (jsiek_at_[hidden])
Date: 2002-08-27 12:28:21

Thanks... I've been meaning to address this issue for a while.

After thinking about this some more, I can't think of any really good
real-world reasons for disallowing self-loops, other than that is
typically done from a graph theory point of view. Also, other's have
complained, saying they wanted to be able to insert self loops.

I'll remove that assert.

Cheers,
Jeremy

On Tue, 27 Aug 2002, Chris Russell wrote:
cdr> Just a quick mention:
cdr>
cdr> A call to add_edge with u == v causes an assertion if Directed ==
cdr> undirectedS.
cdr>
cdr> adjacency_list.hpp line 843:
cdr>      assert( u != v ); // don't allow self-loops
cdr>
cdr> ^- boost_1_28_0
cdr>
cdr> Avoiding the assertion is easy enough but this is inconsistent w/section
cdr> 14.1.1 p.220 of the BGL book: "... Also if u and v are descriptors for the
cdr> same vertex (creating self loop) and the graph is undirected, then the edge
cdr> will not be created and the flag will be false."
cdr>
cdr> Am having tons of fun - the BGL and the book are super. Thanks!
cdr>
cdr> - Chris

----------------------------------------------------------------------
 Jeremy Siek                          http://php.indiana.edu/~jsiek/
 Ph.D. Student, Indiana Univ. B'ton   email: jsiek_at_[hidden]
 C++ Booster (http://www.boost.org)   office phone: [phone]
----------------------------------------------------------------------