NAME¶

std::ranges::in_in_out_result - std::ranges::in_in_out_result

Synopsis¶

Defined in header <algorithm>
template< class I1, class I2, class O > (since C++20)
struct in_in_out_result;

ranges::in_in_out_result is a class template that provides a way to store three
iterators as a single unit.

This class template has no base classes or declared members other than those shown
below. Thus it is suitable for use with structured bindings.

All special member functions of this class template are implicitly declared, which
makes specializations be aggregate classes, and propagate triviality,
potentially-throwing-ness, and constexpr-ness of corresponding operations on data
members.

Template parameters¶

I1, I2, O - the types of the iterators that the ranges::in_in_out_result stores.

Data members

Member name Definition
in1 a value (that is supposed to be an iterator) of type I1.
(public member object)
in2 a value (that is supposed to be an iterator) of type I2.
(public member object)
out a value (that is supposed to be an iterator) of type O.
(public member object)

All these members are declared with [[no_unique_address]] attribute.

Member functions¶

std::ranges::in_in_out_result::operator in_in_out_result<II1, II2, OO>

template<class II1, class II2, class OO>

requires std::convertible_to<const I1&, II1> &&
std::convertible_to<const I2&, II2> && (1)
std::convertible_to<const O&, OO>

constexpr operator in_in_out_result<II1, II2, OO>() const &;
template<class II1, class II2, class OO>

requires std::convertible_to<I1, II1> &&
std::convertible_to<I2, II2> && (2)
std::convertible_to<O, OO>

constexpr operator in_in_out_result<II1, II2, OO>() &&;

Converts *this to the result by constructing every data member of the result from
the corresponding member of *this.

1) Equivalent to return {in1, in2, out};.
2) Equivalent to return {std::move(in1), std::move(in2), std::move(out)};.

Standard library¶

The following standard library functions use ranges::in_in_out_result as the return
type:

Algorithm functions
ranges::transform applies a function to a range of elements
(C++20) (niebloid)
ranges::merge merges two sorted ranges
(C++20) (niebloid)
ranges::set_union computes the union of two sets
(C++20) (niebloid)
ranges::set_intersection computes the intersection of two sets
(C++20) (niebloid)
ranges::set_symmetric_difference computes the symmetric difference between two sets
(C++20) (niebloid)

Synopsis¶

namespace std::ranges
{
template<class I1, class I2, class O>
struct in_in_out_result
{
[[no_unique_address]] I1 in1;
[[no_unique_address]] I2 in2;
[[no_unique_address]] O out;

template<class II1, class II2, class OO>
requires std::convertible_to<const I1&, II1> &&
std::convertible_to<const I2&, II2> &&
std::convertible_to<const O&, OO>
constexpr operator in_in_out_result<II1, II2, OO>() const &
{
return {in1, in2, out};
}

template<class II1, class II2, class OO>
requires std::convertible_to<I1, II1> &&
std::convertible_to<I2, II2> &&
std::convertible_to<O, OO>
constexpr operator in_in_out_result<II1, II2, OO>() &&
{
return {std::move(in1), std::move(in2), std::move(out)};
}
};
}

Notes¶

Each standard library algorithm that uses this family of return types declares a new
alias type, e.g. using merge_result = in_in_out_result<I1, I2, O>;.

The names for such aliases are formed by adding the suffix "_result" to the
algorithm's name. So, the return type of std::ranges::merge can be named as
std::ranges::merge_result.

Unlike std::pair and std::tuple, this class template has data members of meaningful
names.

Example¶

// Run this code

#include <algorithm>
#include <array>
#include <iostream>
#include <iterator>
#include <ranges>

void print(auto rem, auto first, auto last)
{
for (std::cout << rem << ": "; first != last; ++first)
std::cout << *first << ' ';
std::cout << '\n';
}

int main()
{
constexpr static auto in1 = {1, 2, 3, 4, 5, 5};
constexpr static auto in2 = {3, 4, 5, 6, 7};
std::array<int, std::size(in1) + std::size(in2)> out;

const auto result = std::ranges::merge(in1, in2, out.begin());
print("in1", in1.begin(), result.in1);
print("in2", in2.begin(), result.in2);
print("out", out.begin(), result.out);
}

Output:¶

in1: 1 2 3 4 5 5
in2: 3 4 5 6 7
out: 1 2 3 3 4 4 5 5 5 6 7

See also¶

pair implements binary tuple, i.e. a pair of values
(class template)
tuple implements fixed size container, which holds elements of possibly different
(C++11) types
(class template)