I wrote a few posts about using concepts. Concepts are a named set of requirements. Let's define a few concepts in this post.
The unification of templates, concepts, and placeholders goes on. This time, I will have a closer look at constrained (concepts) and unconstrained (auto) placeholders in the context of templates.
C++11 has with auto unconstrained placeholders. You can use concepts in C++20 as constrained placeholders. What seems at first glimpse not so thrilling is for me the decisive quantum leap. C++ templates will become an easy to use C++ feature.
We stay in the year 2020. With high probability we will get concepts. Of course, waterproof statements about the future are difficult but the statement is from Bjarne Stroustrup (Meeting C++ 2016 at Berlin).
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