std::ranges::in_fun_result

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Technical specifications

Symbols index

External libraries

 

Constrained algorithms

Non-modifying sequence operations
ranges::all_ofranges::any_ofranges::none_of ranges::for_each ranges::for_each_n ranges::lexicographical_compare      ranges::adjacent_find	ranges::countranges::count_if ranges::mismatch ranges::equal ranges::containsranges::contains_subrange (C++23)(C++23)	ranges::findranges::find_ifranges::find_if_not ranges::find_lastranges::find_last_ifranges::find_last_if_not (C++23)(C++23)(C++23)	ranges::find_end ranges::find_first_of ranges::search ranges::search_n ranges::starts_with (C++23) ranges::ends_with (C++23)
Modifying sequence operations
ranges::copyranges::copy_if ranges::copy_n ranges::copy_backward ranges::move ranges::move_backward ranges::shift_leftranges::shift_right (C++23)(C++23)   ranges::transform	ranges::fill ranges::fill_n ranges::generate ranges::generate_n ranges::swap_ranges ranges::shuffle ranges::sample	ranges::removeranges::remove_if ranges::replaceranges::replace_if ranges::reverse ranges::rotate ranges::unique	ranges::remove_copyranges::remove_copy_if ranges::replace_copyranges::replace_copy_if ranges::reverse_copy ranges::rotate_copy ranges::unique_copy
Partitioning operations
ranges::is_partitioned ranges::partition_point	ranges::partition ranges::partition_copy	ranges::stable_partition
Sorting operations
ranges::is_sorted ranges::is_sorted_until	ranges::sort ranges::stable_sort	ranges::partial_sort ranges::partial_sort_copy	ranges::nth_element
Binary search operations (on sorted ranges)
ranges::lower_bound	ranges::upper_bound	ranges::binary_search	ranges::equal_range
Set operations (on sorted ranges)
ranges::merge ranges::inplace_merge	ranges::set_difference ranges::set_intersection	ranges::set_symmetric_difference    ranges::set_union	ranges::includes
Heap operations
ranges::is_heap ranges::is_heap_until	ranges::make_heap ranges::sort_heap	ranges::push_heap ranges::pop_heap
Minimum/maximum operations
ranges::max ranges::max_element	ranges::min ranges::min_element	ranges::minmax ranges::minmax_element	ranges::clamp
Permutation operations
ranges::is_permutation	ranges::next_permutation	ranges::prev_permutation
Numeric operations
ranges::iota (C++23)
Fold operations
ranges::fold_left (C++23) ranges::fold_left_first (C++23)	ranges::fold_right (C++23) ranges::fold_right_last (C++23)	ranges::fold_left_with_iter (C++23) ranges::fold_left_first_with_iter (C++23)
Operations on uninitialized storage
ranges::construct_at ranges::destroy ranges::destroy_n ranges::destroy_at	ranges::uninitialized_copy    ranges::uninitialized_move ranges::uninitialized_fill	ranges::uninitialized_copy_n    ranges::uninitialized_move_n ranges::uninitialized_fill_n	ranges::uninitialized_default_construct ranges::uninitialized_default_construct_n    ranges::uninitialized_value_construct ranges::uninitialized_value_construct_n
Return types
ranges::in_fun_result ranges::in_in_result ranges::in_found_result	ranges::in_out_result ranges::in_in_out_result	ranges::in_out_out_result ranges::min_max_result	ranges::out_value_result (C++23) ranges::in_value_result (C++23)

 

Return types of constrained algorithms

Return types

ranges::in_found_result

ranges::in_fun_result

ranges::in_in_out_result

ranges::in_in_result

ranges::in_out_out_result

ranges::in_out_result

ranges::in_value_result (C++23)

ranges::min_max_result

ranges::out_value_result (C++23)

 

Defined in header <algorithm>
template< class I, class F > struct in_fun_result;		(since C++20)

ranges::in_fun_result is a class template that provides a way to store an iterator and a function object 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

I	-	the type of the iterator that the ranges::in_fun_result stores.
F	-	the type of the function object that the ranges::in_fun_result stores.

Data members

std::ranges::in_fun_result::in

[[no_unique_address]] I in;

a value (that is supposed to be an iterator)

std::ranges::in_fun_result::fun

[[no_unique_address]] F fun;

a value (that is supposed to be a function object)

Member functions

std::ranges::in_fun_result::operator in_fun_result<I2, F2>

template<class I2, class F2> requires std::convertible_to<const I&, I2> && std::convertible_to<const F&, F2> constexpr operator in_fun_result<I2, F2>() const &;	(1)
template<class I2, class F2> requires std::convertible_to<I, I2> && std::convertible_to<F, F2> constexpr operator in_fun_result<I2, F2>() &&;	(2)

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

1) Equivalent to return {in, fun};.

2) Equivalent to return {std::move(in), std::move(fun)};.

Standard library

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

Algorithm functions
ranges::for_each (C++20)	applies a function to a range of elements (niebloid)
ranges::for_each_n (C++20)	applies a function object to the first N elements of a sequence (niebloid)

Synopsis

namespace std::ranges
{
    template<class I, class F>
    struct in_fun_result
    {
        [[no_unique_address]] I in;
        [[no_unique_address]] F fun;
 
        template<class I2, class F2>
        requires std::convertible_to<const I&, I2> && std::convertible_to<const F&, F2>
        constexpr operator in_fun_result<I2, F2>() const &
        {
            return {in, fun};
        }
 
        template<class I2, class F2>
        requires std::convertible_to<I, I2> && std::convertible_to<F, F2>
        constexpr operator in_fun_result<I2, F2>() &&
        {
            return {std::move(in), std::move(fun)};
        }
    };
}

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 <iostream>
#include <iterator>
#include <ranges>
 
int main()
{
    int v[] {1, 2, 3};
 
    const auto [last, negate] = std::ranges::for_each_n(v, std::size(v),
        [](int& x) { return x = -x; });
 
    const auto result = std::ranges::for_each(std::cbegin(v), last,
        [](int x) { std::cout << x << ' '; });
    std::cout << "│ ";
 
    std::ranges::for_each(v, negate);
    std::ranges::for_each(v, result.fun);
    std::cout << '\n';
}

Output:

-1 -2 -3 │ 1 2 3

See also

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