Compilare: main.cpp: In member function 'big big::operator+(const big&) const': main.cpp:62:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < max(v1.size(), v2.size()); i++) { ~~^~~~~~~~~~~~~~~~~~~~~~~~~~~ main.cpp:63:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] sf+= (i < v1.size() ? v1[i] - '0' : 0) + (i < v2.size() ? v2[i] - '0': 0); ~~^~~~~~~~~~~ main.cpp:63:61: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] sf+= (i < v1.size() ? v1[i] - '0' : 0) + (i < v2.size() ? v2[i] - '0': 0); ~~^~~~~~~~~~~