C++Now 2021

The second 1/2 of a two part talk -- more focused on the writing of concepts and the design aspects.

In c++20 concepts have finally arrived. Despite long precedence for concepts via meta-programming in c++, concepts brings new facilities to the table. With implementations in compilers and standard library support we now need to step back and consider how to apply this new tool in real projects. How can we use standard library concepts for daily coding? How do we write concepts? How do we design libraries and frameworks with concepts?
This tutorial will climb up the concepts ladder: what's a concept, using concepts in code, reading concepts, writing concepts, and finally designing with concepts.  First we'll cover the basics of concepts, the concept and requires keywords. Then we'll explore the application of concepts from a library user point of view. Including as a variable declaration, return values, and function parameters. We look at Then we'll survey and apply c++20 standard library concepts to typical development of a typical c++ class.
Next the tutorial will dig into writing concepts. Taking a step by step approach we look at the details of concept definitions.  Refactoring std::sleep_for using concepts expand to types outside of std::chrono lets us zero in on concepts design alternatives for functions. And the creation of an interval concept provides an example of designing a library with multiple types using concepts.

Finally, we'll tie our new knowledge and look at some ways concepts can impact c++ designs.  We'll look back on what design is and the tools concepts bring.  How do concepts fit in with a multi-paradigm design world.  How do they compare to design principles like Liskov substitution that we currenlty use. Finally, we'll look at the serialization design pattern and see how concepts impact the tradeoffs involved.