FreeBSD Manual Pages
std::span::first(3) C++ Standard Libary std::span::first(3) NAME std::span::first - std::span::first Synopsis template< std::size_t Count > constexpr std::span<element_type, Count> first() const; constexpr std::span<element_type, std::dynamic_extent> first( size_type Count ) const; Obtains a span that is a view over the first Count elements of this span. The program is ill-formed if Count > Extent. The behavior is undefined if Count > size(). Return value A span r that is a view over the first Count elements of *this, such that r.data() == this->data() && r.size() == Count. Example // Run this code #include <iostream> #include <span> #include <string_view> void print(std::string_view const title, /* std::ranges::forward_range */ auto const& container) { std::cout << title << "[" << std::size(container) << "]{ "; for (auto const& elem : container) std::cout << elem << ", "; std::cout << "};\n"; } void run_game(std::span<const int> span) { print("span: ", span); std::span<const int, 5> span_first = span.first<5>(); print("span.first<5>(): ", span_first); std::span<const int, std::dynamic_extent> span_first_dynamic = span.first(4); print("span.first(4): ", span_first_dynamic); } int main() { int a[8]{ 1, 2, 3, 4, 5, 6, 7, 8, }; print("int a", a); run_game(a); } Output: int a[8]{ 1, 2, 3, 4, 5, 6, 7, 8, }; span: [8]{ 1, 2, 3, 4, 5, 6, 7, 8, }; span.first<5>(): [5]{ 1, 2, 3, 4, 5, }; span.first(4): [4]{ 1, 2, 3, 4, }; See also last obtains a subspan consisting of the last N elements of the sequence (public member function) subspan obtains a subspan (public member function) http://cppreference.com 2022.07.31 std::span::first(3)
NAME | Synopsis | Return value | Example | Output: | See also
Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=std::span::first&sektion=3&manpath=FreeBSD+Ports+15.0>