[Dune] dune::gridleaflist --> std::string prefix an optional or compulsory argument ?

[Jayesh Badwaik]

Hi,

The following functions from the common/gridinfo.hh file do not take prefix as 
an optional argument but make it compulsory (2.1.1 release) 

    1. template<class G> 
        Dune::gridleaflist(G& grid, std::string prefix)
  
    2. template<class G>
        Dune::gridlevellist(G& grid, std::string prefix) 

while the other function in the same file does 

        template<class G>
        Dune::gridinfo(G& grid, std::string prefix="") does. 

I am wondering whether  this is intended or a bug. 

Thanks 
-- 
Jayesh Badwaik