Compilare: user.cpp: In function ‘int main()’: user.cpp:122:6: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] s[j]=NULL;//'\0'; ^ user.cpp: In function ‘bool Factor()’: user.cpp:73:1: warning: control reaches end of non-void function [-Wreturn-type] } ^ user.cpp: In function ‘int main()’: user.cpp:97:22: warning: ignoring return value of ‘char* fgets(char*, int, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fgets(s,sizeof s,in); ^ user.cpp:124:21: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(in,"%d ",&n); ^ user.cpp:129:26: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(in,"%c ",&x); ^