code: public <E extends V> E popAs(@Nonnull final Class<E> c)
      {
          return c.cast(pop());
      }
docs: Removes the value at the top of the value stack and casts it before
  returning it
  
  @param c the class to cast to
  @param <E> type of the class
  @return the current top value
  @throws IllegalArgumentException the stack is empty
  
  @see #pop()