Beginning C++20: From Novice to Professional

© Ivor Horton and Peter Van Weert 2020

I. Horton, P. Van WeertBeginning C++20https://doi.org/10.1007/978-1-4842-5884-2_21

21. Constrained Templates and Concepts

Ivor Horton¹  and Peter Van Weert²

(1)

Stratford-upon-Avon, Warwickshire, UK

(2)

Kessel-Lo, Belgium

 

Templates define parameterized families of C++ entities such as functions (Chapter 10) or class types (Chapter 17). In practice, templates are mostly parameterized on seemingly arbitrary types. Yet most templates cannot be instantiated for just any type; at least not without error. The binary std::max<>() function template, for instance, can only be instantiated for types that support the < operator. And the std::vector<> and std::optional<> class templates may not be instantiated for reference ...