Compilare: user.cpp: In function ‘int main()’: user.cpp:37:65: warning: NULL used in arithmetic [-Wpointer-arith] if(s[i]=='+' or s[i]=='-' or s[i]=='=' or s[i]==NULL) ^ user.cpp:10:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("ecuatii2.in","r",stdin); ^ user.cpp:11:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("ecuatii2.out","w",stdout); ^ user.cpp:14:22: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d\n",&nr); ^ user.cpp:17:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%s\n",s); ^