code: @Override
      public Object setE(int key, Object value) throws ExpressionException {
  	if (offset + key > arr.length) enlargeCapacity(key);
  	if (key > size) size = key;
  	arr[(offset + key) - 1] = checkValue(value);
  	return value;
      }
docs: set value at defined position
  
  @param key
  @param value
  @return defined value
  @throws ExpressionException