c++ - Overloading operator trouble -

hello i'm trying create program reads in series of infix expressions file until reaches semi-colon or period (a+b.), , output postfix of expression file. i'm having trouble getting overloaded operators work correctly. can give me tips on what's wrong them?

std::istream& operator>>(std::istream& in, expression& x) {     char y;     {         in >> y;         x.ifix += y;         if (y == '.') {             x.last = true;         }     } while (y!= ';' || y!= '.');     x.converttopostfix();      return in; }  std::ostream& operator<<(std::ostream& out, const expression& x) {     out << x.pfix;      return out; } 

this expression true:

while (y != ';' || y != '.'); 

if y ';' , y can not '.', second half true. same other way around when y '.'.

you want

while (y != ';' && y != '.'); 

or, if want express more human:

while (!(y == ';' || y == '.')); 

in other words, "do stuff while y not equal semicolon or dot".

this common mistake when combining conditions, , 1 worth spending time understand, can spot in future - because make mistake again, guarantee it.