Compilare: main.cpp: In function 'std::string secv2()': main.cpp:37:11: warning: statement has no effect [-Wunused-value] 37 | for ( i; i >= 0; i-- ) | ^ main.cpp: In function 'std::string secv3()': main.cpp:49:11: warning: statement has no effect [-Wunused-value] 49 | for ( i; i >= 0; i-- ) | ^