al property
for the weight and an external property for the distance. For the weight
property we use the <tt>property</tt> class and specify <tt>int</tt> as the type
used to represent weight values and <tt>edge_weight_t</tt> for the property tag
(which is one of the BGL predefined property tags). The weight property is then
used as a template argument for <tt>adjacency_list</tt>.
<p>The <tt>listS</tt> and <tt>vecS</tt> types are selectors that determine the
data structure used inside the <tt>adjacency_list<