Compilare: main.cpp: In function 'void f1()': main.cpp:23:11: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (i < s.size() && s[i] == ',') { ~~^~~~~~~~~~ main.cpp: In function 'void f2()': main.cpp:33:12: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (i < s.size() && ((s[i] >= 'a' && s[i] <= 'z') || (s[i] >= '0' && s[i] <= '9'))) { ~~^~~~~~~~~~