Giriş
A View is something that you apply on a range and performs some operation. A view does not own data and it's time to copy, move, assignment is constant.
Çoğu view için alternatif bir isim de var. Açıklaması
şöyle
In general, you can use a view such as std::views::transform with the alternative name std::transform_view.
Alternatif isimler parametre olarak bir container/view alıyorlar. view olanlar ise "pipe" işareti ile kullanılıyorlar.
Örnek
Şöyle
yaparız İlk kullanımda pipe işareti görülebilir. İkinci kullanımda ise parametre olarak pi container değişkeni geçiliyor.
auto print = [](char x) { std::cout << x; };
int main()
{
constexpr char pi[] { '3', '.', '1', '4', '1', '5', '9', '2', '6', '5' };
std::ranges::for_each(pi | std::ranges::views::take(8), print);
std::cout << '\n';
std::ranges::for_each(std::ranges::take_view{pi, 8}, print);
std::cout << '\n';
}
Örnek
Şöyle
yaparız. Burada alternatif isimler kullanıldığı için parametre olarak bir container/view geçiliyor.
const std::string s{"cosmos"};
const std::ranges::take_view tv{s, 3};
const std::ranges::ref_view rv{tv};
std::cout
<< std::boolalpha
<< "call empty() : " << rv.empty() << '\n'
<< "call size() : " << rv.size() << '\n'
<< "call begin() : " << *rv.begin() << '\n'
<< "call end() : " << *(rv.end()-1) << '\n'
<< "call data() : " << rv.data() << '\n'
<< "call base() : " << rv.base().size() << '\n' // ~> tv.size()
<< "range-for : ";
for (const auto c: rv) {
std::cout << c;
}
std::cout << '\n';
call empty() : false
call size() : 3
call begin() : c
call end() : s
call data() : cosmos
call base() : 3
range-for : cos
std::ranges::views::all - takes all elements
Alternatif : std::ranges::all_view
Örnek ver
std::ranges::views::chunk - C++23 ile geliyor
Örnek
Vector'deki yan yana elemanları pair haline getirmek için şöyle
yaparız.
#include <iostream>
#include <ranges>
#include <vector>
int main()
{
std::vector<int> values = {1,2,3,4,5,6,7,8,9,10};
auto chunk_to_pair = [](auto chunk)
{
return std::pair(*chunk.begin(), *std::next(chunk.begin()));
};
for (auto [first, second] : values | std::ranges::views::chunk(2)
| std::ranges::views::transform(chunk_to_pair))
{
std::cout << first << second << std::endl;
}
}Aynı şeyi std::ranges::views::stride ile şöyle
yaparız#include <iostream>
#include <ranges>
#include <vector>
int main()
{
std::vector<int> values = {1,2,3,4,5,6,7,8,9,10};
auto odds = values | std::ranges::views::drop(0) | std::ranges::views::stride(2);
auto evens = values | std::ranges::views::drop(1) | std::ranges::views::stride(2);
for (auto [first, second] : std::ranges::views::zip(odds, evens))
{
std::cout << first << second << std::endl;
}
}std::ranges::ref_view - takes all elements of another view
Alternatif : Yok
Örnek ver
std::ranges::istream_view - applies operator>> on the view
Alternatif : std::ranges::basic_istream_view
Örnek ver
std::ranges::views::common - converts a view into a std::common_range
Alternatif : std::ranges::common_view
Örnek ver
std::ranges::views::drop - skips the first N elements of another view
Alternatif : std::ranges::drop_view
Örnek ver
std::ranges::views::drop_while - skips the initial elements of another view until the predicate returns false
Alternatif :std::ranges::drop_while_view
Örnek ver
std::ranges::views::elements - creates a view on the N-th element of tuples
Alternatif : std::ranges::elements_view
Örnek ver
std::ranges::views::filter - takes the elements which satisfies the predicate
Alternatif : std::ranges::filter_view
Örnek ver
std::ranges::views::join - joins a view of ranges
Alternatif : std::ranges::join_view
Örnek ver
std::ranges::views::keys - creates a view on the first element of a pair-like values
Alternatif : std::ranges::keys_view
Örnek ver
std::ranges::views::reverse - iterates in reverse order
Alternatif : std::reverse_view
Örnek ver
std::ranges::views::split - splits a view by using a delimiter
Alternatif : std::ranges::split_view
Örnek ver
std::ranges::views::take - takes the first N elements of another view
Alternatif : std::ranges::take_view
Örnek ver
std::ranges::views::take_while - takes the elements of another view as long as the predicate returns true
Alternatif : std::ranges::take_while_view
Örnek ver
std::ranges::views::transform - transforms each element
Alternatif : std::ranges::transform_view
Örnek ver
std::ranges::views::values - creates a view on the second elements of a pair-like values
Alternatif : std::ranges::values_view
Örnek ver
