weight_combine)</tt> 
<blockquote>
  This function is used to combine distances to compute the distance
  of a path. The <tt>DistanceWeightCombineFunction</tt> type must be a model of <a
  href="http://www.sgi.com/tech/stl/BinaryFunction.html">Binary
  Function</a>. The first argument type of the binary function must
  match the value type of the <tt>DistanceMap</tt> property map and
  the second argument type must match the value type of the
  <tt>WeightMap</tt> property map.  The result type must be the s