CppCon 2018: Victor Ciura “Regular Types and Why Do I Care ?”

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“Regular” is not exactly a new concept (pun intended). If we reflect back on STL and its design principles, as best described by Alexander Stepanov in his 1998 “Fundamentals of Generic Programming” paper or his lecture on this topic, from 2002, we see that regular types naturally appear as necessary foundational concepts in programming.
Why do we need to bother with such taxonomies ? Well, the STL now informally assumes such properties about the types it deals with and imposes such conceptual requirements for its data structures and algorithms to work properly. The new Concepts Lite proposal (hopefully part of C++20) is based on precisely defined foundational concepts such as Semiregular, Regular, EqualityComparable, DefaultConstructible, LessThanComparable (strict weak ordering), etc. Formal specification of concepts is an ongoing effort in the ISO C++ Committee and these STL library concepts requirements are being refined as part of Ranges TS proposal (＜experimental/ranges/concepts＞).
Recent STL additions such as string_view, tuple, reference_wrapper, as well as new incoming types for C++20 like std::span raise new questions regarding values types, reference types and non-owning “borrow” types.
Designing and implementing regular types is crucial in everyday programing, not just library design. Properly constraining types and function prototypes will result in intuitive usage; conversely, breaking subtle contracts for functions and algorithms will result in unexpected behavior for the caller.
This talk will explore the relation between Regular types (and other concepts) and STL containers & algorithms with examples, common pitfalls and guidance.
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Victor Ciura, CAPHYON
Software Developer

For over a decade, he designed and implemented several core components and libraries of Advanced Installer.
He’s a regular guest at Computer Science Department of his Alma Mater, University of Craiova, where he gives student lectures & workshops on “Using C++STL for Competitive Programming and Software Development”.
Currently, he spends most of his time working with his talented team on improving and extending the repackaging and virtualization technologies in Advanced Installer IDE, helping clients migrate their Win32 desktop apps to the Windows Store (MSIX).
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[imable]

Glad to see Stepanov's ideas being spread.

[muckvix]

For those who got stuck like me, a "species" turned out to be a very obscure term meaning the set of entities (such as integers) represented by a type.

But by 20 min the speaker still didn't define regular types, far less actually suggest why they matter.