Difference between revisions of "cpp/iterator/unreachable sentinel t"
From cppreference.com
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===Non-member functions=== | ===Non-member functions=== | ||
{{dsc begin}} | {{dsc begin}} | ||
| − | {{dsc tfun | cpp/iterator/unreachable_sentinel_t | inlinemem=true | title=operator== | | + | {{dsc tfun | cpp/iterator/unreachable_sentinel_t | inlinemem=true | title=operator== | compares an {{tt|unreachable_sentinel_t}} with a value of any {{lconcept|weakly_incrementable}} type | notes={{mark c++20}} }} |
{{dsc end}} | {{dsc end}} | ||
Revision as of 06:19, 2 February 2020
| Defined in header <iterator>
|
||
| struct unreachable_sentinel_t; |
(1) | (since C++20) |
| inline constexpr unreachable_sentinel_t unreachable_sentinel{}; |
(2) | (since C++20) |
1)
unreachable_sentinel_t is an empty class type that can be used to denote the “upper bound” of an unbounded interval.2)
unreachable_sentinel is a constant of type unreachable_sentinel_t.Contents |
Non-member functions
| operator== (C++20) |
compares an unreachable_sentinel_t with a value of any weakly_incrementable type (function template) |
operator==(std::unreachable_sentinel_t)
| template<std::weakly_incrementable I> friend constexpr operator==( unreachable_sentinel_t, const I& ) noexcept |
(since C++20) | |
unreachable_sentinel_t can be compared with any weakly_incrementable type and the result is always false.
This function template is not visible to ordinary unqualified or qualified lookup, and can only be found by argument-dependent lookup when std::unreachable_sentinel_t is an associated class of the arguments.
Example
Run this code
#include <cstddef> #include <iterator> #include <algorithm> #include <iostream> template<class CharT> std::size_t ntcts_len(const CharT *s) { return std::ranges::find(s, std::unreachable_sentinel, CharT{}) - s; } int main() { std::cout << ntcts_len("The quick brown fox jumps over the lazy dog.") << '\n'; }
Output:
44
See also
| (C++20) |
a view consisting of a sequence generated by repeatedly incrementing an initial value(class template) (customization point object) |
