Compilare: main.cpp: In function 'int sum()': main.cpp:32:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(position < s.size() && (s[position] == '+' || s[position] == '-')) { ~~~~~~~~~^~~~~~~~~~ main.cpp: In function 'int product()': main.cpp:44:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(position < s.size() && (s[position] == '*' || s[position] == '/')) { ~~~~~~~~~^~~~~~~~~~ main.cpp: In function 'int numberOrSum()': main.cpp:61:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(position < s.size() && '0' <= s[position] && s[position] <= '9') { ~~~~~~~~~^~~~~~~~~~