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Subject: Re: [boost] [multimethods] Proposal: Open Multi-Methods
From: Jean-Louis Leroy (jl_at_[hidden])
Date: 2013-08-31 09:11:08

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.


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