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Showing content from https://cplusplus.github.io/LWG/issue3133 below:

Issue 3133: Modernizing numeric type requirements

This page is a snapshot from the LWG issues list, see the Library Active Issues List for more information and the meaning of C++20 status.

Section: 29.2 [numeric.requirements] Status: C++20 Submitter: Tim Song Opened: 2018-07-05 Last modified: 2021-02-25

29.2 [numeric.requirements] contains some very old wording that hasn't been changed since C++98 except for issue 2699⁽ⁱ⁾. As a result, it is at once over- and under-restrictive. For example:

We can significantly clean up this wording by using the existing named requirements. For ease of review, the following table provides a side-by-side comparison of the current and proposed wording.

Before After A C++ program shall instantiate these components only with a type T that satisfies the following requirements: [Footnote … ] A C++ program shall instantiate these components only with a cv-unqualified object type T that satisfies the Cpp17DefaultConstructible, Cpp17CopyConstructible, Cpp17CopyAssignable, and Cpp17Destructible following requirements (16.4.4.2 [utility.arg.requirements]). : (1.1) — T is not an abstract class (it has no pure virtual member functions); Cpp17DefaultConstructible (1.2) — T is not a reference type;
(1.3) — T is not cv-qualified; Implied by "cv-unqualified object type" (1.4) — If T is a class, it has a public default constructor; Cpp17DefaultConstructible (1.5) — If T is a class, it has a public copy constructor with the signature T::T(const T&); Cpp17CopyConstructible (1.6) — If T is a class, it has a public destructor; Cpp17Destructible (1.7) — If T is a class, it has a public copy assignment operator whose signature is either T& T::operator=(const T&) or T& T::operator=(T); Cpp17CopyAssignable (1.8) — If T is a class, its assignment operator, copy and default constructors, and destructor shall correspond to each other in the following sense:
(1.8.1) — Initialization of raw storage using the copy constructor on the value of T(), however obtained, is semantically equivalent to value-initialization of the same raw storage.
(1.8.2) — Initialization of raw storage using the default constructor, followed by assignment, is semantically equivalent to initialization of raw storage using the copy constructor.
(1.8.3) — Destruction of an object, followed by initialization of its raw storage using the copy constructor, is semantically equivalent to assignment to the original object.
[Note: […] — end note] These requirements are implied by Cpp17CopyConstructible and Cpp17CopyAssignable's requirement that the value of the copy is equivalent to the source. (1.9) — If T is a class, it does not overload unary operator&. omitted now that we have std::addressof

This wording is relative to the post-Rapperswil 2018 working draft.

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