Home - News ( United States | United Kingdom | Italy | Germany ) - Football scores

Showing content from https://cplusplus.github.io/LWG/issue3381 below:

begin and data must agree for contiguous_range

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: 25.4.6 [range.refinements] Status: C++20 Submitter: Casey Carter Opened: 2020-01-25 Last modified: 2021-02-25

Priority: 0

View all other issues in [range.refinements].

View all issues with C++20 status.

Discussion:

The definition of the contiguous_range concept in 25.4.6 [range.refinements]/2 requires that ranges::data(r) be valid for a contiguous_range r, but fails to impose the obvious semantic requirement that to_address(ranges::begin(r)) == ranges::data(r). In other words, data and begin must agree so that [begin(r), end(r)) and the counted range data(r) + [0, size(r)) (this is the new "counted range" specification syntax per working draft issue 2932) denote the same sequence of elements.

[2020-02 Prioritized as IMMEDIATE Monday morning in Prague]

Proposed resolution:

This wording is relative to N4849.

1. Modify 25.4.6 [range.refinements] as indicated:

   -2- contiguous_range additionally requires that the ranges::data customization point (25.3.14 [range.prim.data]) is usable with the range.

   template<class T>
     concept contiguous_range =
       random_access_range<T> && contiguous_iterator<iterator_t<T>> &&
       requires(T& t) {
         { ranges::data(t) } -> same_as<add_pointer_t<range_reference_t<T>>>;
       };
   

   -?- Given an expression t such that decltype((t)) is T&, T models contiguous_range only if (to_address(ranges::begin(t)) == ranges::data(t)).

   -3- The common_range concept […]

RetroSearch is an open source project built by @garambo | Open a GitHub Issue

Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo

HTML: 3.2 | Encoding: UTF-8 | Version: 0.7.4