Compilare: user.cpp: In function ‘void shutingYard(std::__cxx11::string)’: user.cpp:37:12: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i< I.size()) ^ user.cpp:44:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while( i+1 < I.size() && isdigit(I[i+1])) ^ user.cpp:56:93: warning: array subscript has type ‘char’ [-Wchar-subscripts] while ( operators.size()>0 && isOperator(operators.top())&& pre[operators.top()]>=pre[(unsigned int)token]) ^ user.cpp: In function ‘void evalRPlr()’: user.cpp:84:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0 ; i < postFix.size(); i++) ^ user.cpp: In function ‘int evaluateExpr(int, char, int)’: user.cpp:30:1: warning: control reaches end of non-void function [-Wreturn-type] } ^