std::ranges::in_fun_result
Defined in header <algorithm>
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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.
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F | - | the type of the function object that the ranges::in_fun_result stores.
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Data members
std::ranges::in_fun_result::in
[[no_unique_address]] I in; |
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a value (that is supposed to be an iterator)
std::ranges::in_fun_result::fun
[[no_unique_address]] F fun; |
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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> |
(1) | |
template<class I2, class F2> requires std::convertible_to<I, I2> && std::convertible_to<F, F2> |
(2) | |
Converts *this to the result by constructing every data member of the result from the corresponding member of *this.
Standard library
The following standard library functions use ranges::in_fun_result
as the return type:
Algorithm functions | |
(C++20) |
applies a function to a range of elements (niebloid) |
(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
#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
implements binary tuple, i.e. a pair of values (class template) | |
(C++11) |
implements fixed size container, which holds elements of possibly different types (class template) |