[Boost-users] put problem

Hi I'm new user of boost library I tried to create a graph but I can't modify the weight_map of this graph. In my code: boost::property_map::type weight_map=get(boost::edge_weight,ft); | | put(weight_map,*eit,100); at compile time I've for command "put": "../property_map.hpp:319: error: invalid lvalue in assignment Best regards -Bombielfil-