After your first named argument, you need to use named arguments for the rest of the argument list:
metric_tsp_approx(g_init, weight_map(...).vertex_index_map(...).visitor(...));
Fixing that might fix your compilation errors.
-- Jeremiah Willcock
Jeremiah : could you explain why you need named arguments ? I find that very confusing ! Also, I'm having trouble creating a visitor. I tried : metric_tsp_approx(g_init, weight_map(get(&Road::length, g_init)).vertex_index_map(get(&City::id, g_init)) .make_tsp_tour_visitor(back_inserter(c))); But compiling raises the error : has no member named ‘make_tsp_tour_visitor’ Should I create a class for the visitor ? Albert : I have included a small example as an attached file. -- Alexis Praga, PhD Student (CERFACS) GPG key : AD4A AF6D BB5C 042F 9422 1223 06E1 C1BF E287 65D0