Compilare: main.cpp: In function 'int E(const string&, int&)': main.cpp:35:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (i < e.size()) ~~^~~~~~~~~~ main.cpp:46:19: warning: value computed is not used [-Wunused-value] a == P(e, i); ~~^~~~~~~~~~ main.cpp: In function 'int P(const string&, int&)': main.cpp:59:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (i < e.size()) ~~^~~~~~~~~~ main.cpp: In function 'int C(const string&, int&)': main.cpp:96:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (i < e.size() && std::isdigit(e[i])) ~~^~~~~~~~~~ main.cpp: In function 'int E(const string&, int&)': main.cpp:54:1: warning: control reaches end of non-void function [-Wreturn-type] } ^