Compilare: user.cpp: In function ‘void value()’: user.cpp:19:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(p < s.size() && (s[p] >= 'a' && s[p] <= 'z')) ^ user.cpp:22:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(p < s.size() && isdigit(s[p])) ^ user.cpp: In function ‘void expr()’: user.cpp:30:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(p < s.size()) { ^ user.cpp:35:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(p < s.size() && isdigit(s[p])) ^ user.cpp: In function ‘int main()’: user.cpp:57:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < t.size(); i++) { ^