Compilare: user.cpp: In function ‘void formarenumar()’: user.cpp:19:75: warning: NULL used in arithmetic [-Wpointer-arith] while(sir[i]!='-'&&sir[i]!='+'&&sir[i]!='x'&&sir[i]!='='&&sir[i]!=NULL) ^ user.cpp: In function ‘void prelucrare()’: user.cpp:65:19: warning: NULL used in arithmetic [-Wpointer-arith] while(sir[i]!=NULL) ^ user.cpp:73:20: warning: NULL used in arithmetic [-Wpointer-arith] if(sir[i]==NULL) ^ user.cpp: In function ‘int main()’: user.cpp:103:25: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] sir[strlen(sir)]=NULL; ^