Home - News ( United States | United Kingdom | Italy | Germany ) - Football scores

Showing content from https://en.cppreference.com/w/cpp/algorithm/../symbol_index/../algorithm/ranges/move_backward.html below:

std::ranges::move_backward, std::ranges::move_backward_result - cppreference.com

Call signature

Helper types

Moves the elements in the range, defined by

, to another range

, where

. The elements are moved in reverse order (the last element is moved first), but their relative order is preserved. The behavior is undefined if

is within

. In such a case,

may be used instead.

The elements in the moved-from range will still contain valid values of the appropriate type, but not necessarily the same values as before the move, as if using *(d_last - n) = ranges::iter_move(last - n) for each integer n, where 0 ≤ n < N.

The function-like entities described on this page are algorithm function objects (informally known as niebloids), that is:

• Explicit template argument lists cannot be specified when calling any of them.
• None of them are visible to argument-dependent lookup.
• When any of them are found by normal unqualified lookup as the name to the left of the function-call operator, argument-dependent lookup is inhibited.

{last, d_last - N}.

1) Exactly N move assignments.

When moving overlapping ranges, ranges::move is appropriate when moving to the left (beginning of the destination range is outside the source range) while ranges::move_backward is appropriate when moving to the right (end of the destination range is outside the source range).

struct move_backward_fn
{
    template<std::bidirectional_iterator I1, std::sentinel_for<I1> S1,
             std::bidirectional_iterator I2>
    requires std::indirectly_movable<I1, I2>
    constexpr ranges::move_backward_result<I1, I2>
        operator()(I1 first, S1 last, I2 d_last) const
    {
        auto i {last};
        for (; i != first; *--d_last = ranges::iter_move(--i))
        {}
        return {std::move(last), std::move(d_last)};
    }
 
    template<ranges::bidirectional_range R, std::bidirectional_iterator I>
    requires std::indirectly_movable<ranges::iterator_t<R>, I>
    constexpr ranges::move_backward_result<ranges::borrowed_iterator_t<R>, I>
        operator()(R&& r, I d_last) const
    {
        return (*this)(ranges::begin(r), ranges::end(r), std::move(d_last));
    }
};
 
inline constexpr move_backward_fn move_backward {};

#include <algorithm>
#include <iostream>
#include <string>
#include <string_view>
#include <vector>
 
using Vec = std::vector<std::string>;
 
void print(std::string_view rem, Vec const& vec)
{
    std::cout << rem << "[" << vec.size() << "]: ";
    for (const std::string& s : vec)
        std::cout << (s.size() ? s : std::string{"·"}) << ' ';
    std::cout << '\n';
}
 
int main()
{
    Vec a{"▁", "▂", "▃", "▄", "▅", "▆", "▇", "█"};
    Vec b(a.size());
 
    print("Before move:\n" "a", a);
    print("b", b);
 
    std::ranges::move_backward(a, b.end());
 
    print("\n" "Move a >> b:\n" "a", a);
    print("b", b);
 
    std::ranges::move_backward(b.begin(), b.end(), a.end());
    print("\n" "Move b >> a:\n" "a", a);
    print("b", b);
 
    std::ranges::move_backward(a.begin(), a.begin()+3, a.end());
    print("\n" "Overlapping move a[0, 3) >> a[5, 8):\n" "a", a);
}

Possible output:

Before move:
a[8]: ▁ ▂ ▃ ▄ ▅ ▆ ▇ █
b[8]: · · · · · · · ·
 
Move a >> b:
a[8]: · · · · · · · ·
b[8]: ▁ ▂ ▃ ▄ ▅ ▆ ▇ █
 
Move b >> a:
a[8]: ▁ ▂ ▃ ▄ ▅ ▆ ▇ █
b[8]: · · · · · · · ·
 
Overlapping move a[0, 3) >> a[5, 8):
a[8]: · · · ▄ ▅ ▁ ▂ ▃

RetroSearch is an open source project built by @garambo | Open a GitHub Issue

Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo

HTML: 3.2 | Encoding: UTF-8 | Version: 0.7.4