Difference between revisions of "cpp/container/span/dynamic extent"
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| − | + | Since {{tt|std::size_t}} is an unsigned type, an equivalent definition is: | |
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Revision as of 07:37, 29 October 2021
| Defined in header <span>
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| inline constexpr std::size_t dynamic_extent = std::numeric_limits<std::size_t>::max(); |
(since C++20) | |
std::dynamic_extent is a constant of type std::size_t that is used to differentiate std::span of static and dynamic extent.
Note
Since std::size_t is an unsigned type, an equivalent definition is:
inline constexpr std::size_t dynamic_extent = -1;
See integral conversions.
Example
Run this code
#include <array> #include <cassert> #include <cstddef> #include <iostream> #include <span> #include <string_view> #include <vector> int main() { auto print = [](std::string_view const name, std::size_t ex) { std::cout << name << ", "; if (ex == std::dynamic_extent) { std::cout << "dynamic extent\n"; } else { std::cout << "static extent = " << ex << '\n'; } }; int a[]{1,2,3,4,5}; std::span span1{a}; print("span1", span1.extent); std::span<int, std::dynamic_extent> span2{a}; print("span2", span2.extent); std::array ar{1,2,3,4,5}; std::span span3{ar}; print("span3", span3.extent); std::vector v{1,2,3,4,5}; std::span span4{v}; print("span4", span4.extent); }
Output:
span1, static extent = 5 span2, dynamic extent span3, static extent = 5 span4, dynamic extent
See also
| (C++20) |
a non-owning view over a contiguous sequence of objects (class template) |
