Compilare: main.cpp: In function 'int eval(std::__cxx11::string, std::__cxx11::string, int)': main.cpp:24:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < b1.length(); ++i) ~~^~~~~~~~~~~~~ main.cpp:27:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < b1.length(); ++i) ~~^~~~~~~~~~~~~ main.cpp:45:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < b1.length(); ++i){ ~~^~~~~~~~~~~~~