Compilare: main.cpp: In function 'int sum_diff()': main.cpp:13:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(ind<s.size() and (s[ind]=='+' or s[ind]=='-')) ~~~^~~~~~~~~ main.cpp: In function 'int prod_imp()': main.cpp:24:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(ind<s.size() and (s[ind]=='*' or s[ind]=='/')) ~~~^~~~~~~~~ main.cpp: In function 'int term()': main.cpp:42:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(ind<s.size() and '0'<=s[ind] and s[ind]<='9') ~~~^~~~~~~~~