Compilare: user.cpp: In function ‘bool equals(std::string, std::string)’: user.cpp:10:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < a.length(); i++) { ^ user.cpp: In function ‘bool contains(std::string, std::string)’: user.cpp:23:53: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < in.length() - str.length(); i++) { ^ user.cpp: In function ‘int main()’: user.cpp:93:49: warning: ‘length’ may be used uninitialized in this function [-Wmaybe-uninitialized] if(index == -1 || k > length) { ^