Compilare: main.cpp: In function 'void add(std::__cxx11::string&, std::__cxx11::string)': main.cpp:9:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(++ind<=a.size()&&indb<b.size()){ ~~~~~^~~~~~~~~~ main.cpp:9:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(++ind<=a.size()&&indb<b.size()){ ~~~~^~~~~~~~~