Compilare: main.cpp: In function 'int nr(int&)': main.cpp:11:47: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while('0'<=c[st+1] && c[st+1]<='9' && st+1<=strlen(c)) ~~~~^~~~~~~~~~~ main.cpp: In function 'int prod(int&, int)': main.cpp:21:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(c[st]=='*' || c[st]=='/' && st+1<=strlen(c)) ~~~~^~~~~~~~~~~ main.cpp:21:36: warning: suggest parentheses around '&&' within '||' [-Wparentheses] while(c[st]=='*' || c[st]=='/' && st+1<=strlen(c)) ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~