[Boost-users] [concept checking] BOOST_CONCEPT_REQUIRES for constructors and template specialization in function of concept implementation

Hi, I have two questions regarding concept checking. The first is whether BOOST_CONCEPT_REQUIRES can be used for constructors and how. The second is to know if it's possible to specialize templates, or perform conditional compilation in some way, for object implementing some concept or not. For example, if I have an algorithm for directed graphs that requires IncidenceGraphConcept, can I specialize the code for graphs that implement BidirecionalGraphConcept? Thanks, Juan Farré