Compilare: main.cpp: In function 'std::__cxx11::string replaceOperators(std::__cxx11::string)': main.cpp:23:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(found!=string::npos) ~~~~~^~~~~~~~ main.cpp:29:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(found!=string::npos) ~~~~~^~~~~~~~ main.cpp:35:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(found!=string::npos) ~~~~~^~~~~~~~ main.cpp:41:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(found!=string::npos) ~~~~~^~~~~~~~ main.cpp:47:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(found!=string::npos) ~~~~~^~~~~~~~ main.cpp:53:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(found!=string::npos) ~~~~~^~~~~~~~ main.cpp:57:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = found;!isLetter(a[i]) && i<a.size();i++); ~^~~~~~~~~ main.cpp: In function 'std::__cxx11::string infixToPostFix(std::__cxx11::string)': main.cpp:84:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0;i<a.size();i++) ~^~~~~~~~~ main.cpp: In function 'void buildIndexTable(std::__cxx11::string)': main.cpp:117:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0;i<a.size();i++) ~^~~~~~~~~ main.cpp: In function 'std::__cxx11::string replaceVariables(std::__cxx11::string)': main.cpp:128:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0;i<a.size();i++) ~^~~~~~~~~ main.cpp: In function 'bool evaluate(std::__cxx11::string)': main.cpp:139:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0;i<a.size();i++) ~^~~~~~~~~