Compilare: main.cpp: In member function 'int expression::E()': main.cpp:17:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (i < e.size() && e[i] == '+' || e[i] == '-') ~~^~~~~~~~~~ main.cpp:17:29: warning: suggest parentheses around '&&' within '||' [-Wparentheses] while (i < e.size() && e[i] == '+' || e[i] == '-') ~~~~~~~~~~~~~^~~~~~~~~~~~~~ main.cpp: In member function 'int expression::P()': main.cpp:38:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (i < e.size() && e[i] == '*' || e[i] == '/') ~~^~~~~~~~~~ main.cpp:38:29: warning: suggest parentheses around '&&' within '||' [-Wparentheses] while (i < e.size() && e[i] == '*' || e[i] == '/') ~~~~~~~~~~~~~^~~~~~~~~~~~~~ main.cpp: In member function 'int expression::C()': main.cpp:73:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (i < e.size() && std::isdigit(e[i])) ~~^~~~~~~~~~