std::unreachable_sentinel_t, std::unreachable_sentinel
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.
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 bool operator==( unreachable_sentinel_t, const I& ) noexcept
{ return false; } |
(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
#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) |
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https://en.cppreference.com/w/cpp/iterator/unreachable_sentinel_t
