title: Handling extra operators in Shunting-yard
body: <p>Given an input like this: <code>3+4+</code>
  Algorithm turns it in to <code>3 4 + +</code></p>
  
  <p>I can find the error when it's time to execute the postfix expression.
  But, is it possible to spot this during the conversion? </p>
  
  <p>(Wikipedia article and internet articles I've read do not handle this case)</p>
  
  <p>Thank you</p>