Compilare: main.cpp: In function 'bool isNotOperator()': main.cpp:33:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (k + 2 >= s.size()) { ~~~~~~^~~~~~~~~~~ main.cpp: In function 'bool evalLinear(std::vector<bool>&, std::vector<char>&)': main.cpp:50:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < ops.size(); ++i) { ~~^~~~~~~~~~~~ main.cpp: In function 'char nextOperator()': main.cpp:72:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (k + 2 < s.size() && s[k] == 'A' && s[k + 1] == 'N' && s[k + 2] == 'D') { ~~~~~~^~~~~~~~~~ main.cpp: In function 'bool nextTerm()': main.cpp:82:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (k + 3 < s.size() && s[k] == 'T' && s[k + 1] == 'R' && s[k + 2] == 'U' && s[k + 3] == 'E') { ~~~~~~^~~~~~~~~~ main.cpp:87:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (k + 4 < s.size() && s[k] == 'F' && s[k + 1] == 'A' && s[k + 2] == 'L' && s[k + 3] == 'S' && s[k + 4] == 'E') { ~~~~~~^~~~~~~~~~ main.cpp: In function 'int eval()': main.cpp:106:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (k < s.size()) { ~~^~~~~~~~~~