[Boost-users] [BGL] null edge descriptor

Subject: [Boost-users] [BGL] null edge descriptor
From: Ireneusz Szcześniak (irek.szczesniak_at_[hidden])
Date: 2017-05-01 08:18:33

Hi,

I'm using Boost Graph Library (BGL), and I need a null edge.  For 
years I was using G::edge_descriptor(), i.e., a default-constructed 
edge descriptor, and the code was working.  However, I wonder if it is 
correct.

Are all default-constructed edges equal?   If I get a 
default-constructed edge descriptor e1 at some point in code, and 
another default-constructed edge descriptor e2 at some other point in 
code, will there descriptors always equal, i.e., will e1 == e2 always 
hold?

Is it guaranteed that a default-constructed edge does not refer to an 
existing edge in a graph?

Best,
Irek