Eroare de compilare: user.cpp: In function ‘void evaluateExpr()’: user.cpp:46:10: warning: array subscript has type ‘char’ [-Wchar-subscripts] nr[l++] = expr[i]; ^ user.cpp: In function ‘int main()’: user.cpp:92:19: error: ‘strlen’ was not declared in this scope len = strlen(expr) - 1; ^ user.cpp:88:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("evaluare.in","r",stdin); ^ user.cpp:89:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("evaluare.out","w",stdout); ^ user.cpp:91:32: warning: ignoring return value of ‘char* fgets(char*, int, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fgets(expr,sizeof(expr),stdin); ^