On 31-Aug-13 13:17, Bjorn Reese wrote:
On 08/31/2013 01:08 PM, Edward Diener wrote:
The issue seems to be to justify practical use of multi-methods over traditional OO programming with virtual functions. Remember that the latter has been the core of OO programming for decades. I do not know even how to think about designing software using multi-methods as opposed to virtual functions. Without some serious practical benefits
The example that Alexandrescu is using in his Modern C++ Design, chapter 11 on multimethods, is collision detection.
In the second article in my series on open multi-methods (to be published soon on Code Project), I examine another example: matrix addition. I also argue that open methods (multi or not, i.e. whether they have one virtual argument or several) are superior to virtual functions when it comes to modularity, extensibility and encapsulation. A friend told me that practical applications of multi-methods are common in adventure game programming, where constructs like "do this to that with something" abound. Languages like TADS support multi-methods for that purpose. See also my example (in my lib's docs) of a three argument method "approve(expense, role, reason)" in an expense approval system. Finally, multi-methods are not a recent idea. They have been around for 30 years and are available in many languages. Jean-Louis