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While we wait for this year’s event, we’re featuring videos of some of the 100+ talks from CppCon 2017 for you to enjoy. Here is today’s feature:

Agent based class design

by Odin Holmes

(watch on YouTube) (watch on Channel 9)

Summary of the talk:

Abstracting a set of functionalities into a class which provides a higher level interface often requires tough design decisions. Users who do not have the exact requirements for which the abstraction is optimized will suffer a syntactic or run time overhead as a result. Alexandrescu's famous "policy-based design" provides a mechanism to allow the user to extend and customize an existing abstraction in order to fine-tune its functionality for many different use cases. This is however limited to use cases where each policy more or less represents a compile time strategy pattern.

Alas, not everything is a strategy pattern. In this talk I will explore the viability of a more agent-pattern-like paradigm where each policy knows its requirements and publishes its capabilities. In this paradigm, glue code connecting any valid set of policies is automatically generated using template metaprogramming. This allows much more powerful customizations while maintaining static linkage.