Compilare: user.cpp: In function ‘int base(std::string, int)’: user.cpp:14:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<s.length();++i){ ^ user.cpp:22:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<s.length();++i){ ^ user.cpp:30:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<s.length();++i){ ^ user.cpp: At global scope: user.cpp:45:10: warning: ISO C++ forbids declaration of ‘main’ with no type [-Wreturn-type] main(void) ^