std::span<T,Extent>::first
From cppreference.com
| template< std::size_t Count > constexpr std::span<element_type, Count> first() const; |
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| constexpr std::span<element_type, std::dynamic_extent> first( std::size_t Count ) const; |
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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
obtains a subspan consisting of the last N elements of the sequence (public member function) | |
| obtains a subspan (public member function) |
