std::ranges::views::single, std::ranges::single_view
Defined in header <ranges>
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||
template< std::copy_constructible T > requires std::is_object_v<T> |
(1) | (since C++20) |
namespace views { inline constexpr /*unspecified*/ single = /*unspecified*/; |
(2) | (since C++20) |
Typical implementations of single_view
store a single member of type semiregular_box<T>
. For description purposes, this member is hereinafter called value_
.
The lifetime of the element is bound to the parent single_view
. Copying single_view
makes a copy of the element.
Contents |
[edit] Expression-equivalent
Expression e is expression-equivalent to expression f, if e and f have the same effects, either are both potentially-throwing or are both not potentially-throwing (i.e. noexcept(e) == noexcept(f)), and either are both constant subexpressions or are both not constant subexpressions.
[edit] Member functions
(constructor) |
constructs a single_view (public member function) |
begin |
returns a pointer to the element (public member function) |
end |
returns a pointer past the element (public member function) |
size [static] |
returns 1 (one) (public static member function) |
data |
returns a pointer to the element (public member function) |
std::ranges::single_view::single_view
single_view() = default; |
(1) | |
constexpr explicit single_view( const T& t ); |
(2) | |
constexpr explicit single_view( T&& t ); |
(3) | |
template< class... Args > requires std::constructible_from<T, Args...> |
(4) | |
Constructs a single_view
.
value_
.value_
with t.value_
with std::move(t).std::ranges::single_view::begin
constexpr T* begin() noexcept; constexpr const T* begin() const noexcept; |
||
Equivalent to return data();.
std::ranges::single_view::end
constexpr T* end() noexcept; constexpr const T* end() const noexcept; |
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Equivalent to return data() + 1;.
std::ranges::single_view::size
static constexpr std::size_t size() noexcept; |
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Equivalent to return 1;.
This is a static function. This makes single_view
model /*tiny-range*/ as required by split_view
.
std::ranges::single_view::data
constexpr T* data() noexcept; constexpr const T* data() const noexcept; |
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Returns value_.operator->()
.
[edit] Example
#include <iostream> #include <ranges> #include <string> #include <tuple> int main() { std::ranges::single_view sv1{3.1415}; // uses (const T&) constructor std::cout << "1) *sv1.data(): " << *sv1.data() << '\n' << "2) *sv1.begin(): " << *sv1.begin() << '\n' << "3) sv1.size(): " << sv1.size() << '\n' << "4) distance: " << std::distance(sv1.begin(), sv1.end()) << '\n'; std::string str{"C++20"}; std::cout << "5) str = \"" << str << "\"\n"; std::ranges::single_view sv2{std::move(str)}; // uses (T&&) constructor std::cout << "6) *sv2.data(): \"" << *sv2.data() << "\"\n" << "7) str = \"" << str << "\"\n"; std::ranges::single_view<std::tuple<int, double, std::string>> sv3{std::in_place, 42, 3.14, "😄"}; // uses (std::in_place_t, Args&&... args) std::cout << "8) sv3 keeps a tuple: { " << std::get<0>(sv3[0]) << ", " << std::get<1>(sv3[0]) << ", " << std::get<2>(sv3[0]) << " }\n"; }
Output:
1) *sv1.data(): 3.1415 2) *sv1.begin(): 3.1415 3) sv1.size(): 1 4) distance: 1 5) str = "C++20" 6) *sv2.data(): "C++20" 7) str = "" 8) sv3 keeps a tuple: { 42, 3.14, 😄 }
[edit] See also
an empty view with no elements (class template) (variable template) | |
a view over the subranges obtained from splitting another view using a delimiter (class template) (range adaptor object) |