but would have caused an efficiency cnocern

4+11*8

Should be 92.  But can be viewed as ambigious - must paranthesize it. 

Let's make a function that does this: 
47 + 8 x = (4+7)x8 = 88
478 x+ = (7x8)+4 = 60

//for each operator, takes two previous numbers and does something to it

bool evaluate(Stack& memory, string expr) {

 for(int i=0; i    if(isOperator(expr[i])) {
      if(memory.size()<2) return false;
      int second = memory.pop();
      int first = memory.pop();
      memory.push(combine(first, expr[i], second));
   } else {
      memory.push(expr[i] - 'o');
   }
 }
 return memory.size()==1;
}

int combine(int one, char op, int two) {
  switch(op) {
    case '+': return one+two;
    case '-': return one-two;
    case '*': return one*two;
    case '/': return one/two;
    case '%': return one%two;
  }

}

proves how reducing interface can actually have benefits

can be used in circumstances where you go in circles for something, and the size of the circle is dynamically changing

int lastKilled=0;
int nextToLastKilled=0;
determineSurvivors(42,7,lastKilled,nextToLastKilled);

void ds(int numPeople, int numToSpare, int& lastKilled, int& nextToLastKilled) {
   Queue<int> circle;
   for(int n=1; n<=numPeople; n++)  circle.enqueue(n);
   while(!circle.isEmpty())  {
      for(int i=0; i<numToSpare; i++) {
         circle.enqueue(circle.dequeue());
      }
      nextToLastKilled = lastKilled;
      lastKilled = circle.dequeue();
}