Compilare: main.cpp: In function 'long int addOrSub()': main.cpp:18:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (position < input.size() && (input[position] == '+' || input[position] == '-')) ~~~~~~~~~^~~~~~~~~~~~~~ main.cpp: In function 'long int factor()': main.cpp:37:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (position < input.size() && (input[position] == '*' || input[position] == '/')) ~~~~~~~~~^~~~~~~~~~~~~~ main.cpp: In function 'long int term()': main.cpp:73:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (position < input.size() && '0' <= input[position] && input[position] <= '9') ~~~~~~~~~^~~~~~~~~~~~~~