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std::ranges::sort(3) C++ Standard Libary std::ranges::sort(3) NAME std::ranges::sort - std::ranges::sort Synopsis Defined in header <algorithm> Call signature template< std::random_access_iterator I, std::sentinel_for<I> S, class Comp = ranges::less, class Proj = std::identity > requires std::sortable<I, Comp, Proj> (1) (since C++20) constexpr I sort( I first, S last, Comp comp = {}, Proj proj = {} ); template< ranges::random_access_range R, class Comp = ranges::less, class Proj = std::identity > (2) (since C++20) requires std::sortable<ranges::iterator_t<R>, Comp, Proj> constexpr ranges::borrowed_iterator_t<R> sort( R&& r, Comp comp = {}, Proj proj = {} ); Sorts the elements in the range [first, last) in non-descending or- der. The order of equivalent elements is not guaranteed to be preserved. A sequence is sorted with respect to a comparator comp if for any iterator it pointing to the sequence and any non-negative integer n such that it + n is a valid iterator pointing to an element of the sequence, std::invoke(comp, std::invoke(proj, *(it + n)), std::invoke(proj, *it)) evaluates to false. 1) Elements are compared using the given binary comparison function comp. 2) Same as (1), but uses r as the source range, as if using ranges::begin(r) as first and ranges::end(r) as last. The function-like entities described on this page are niebloids, that is: * Explicit template argument lists may not be specified when call- ing any of them. * None of them is visible to argument-dependent lookup. * When one of them is found by normal unqualified lookup for the name to the left of the function-call operator, it inhibits argument-dependent lookup. In practice, they may be implemented as function objects, or with special compiler extensions. Parameters first, last - iterator-sentinel defining the range to sort r - the range to sort comp - comparison to apply to the projected elements proj - projection to apply to the elements Return value An iterator equal to last. Complexity \(\scriptsize \mathcal{O}(N\cdot\log{(N)})\)(Nlog(N)) comparisons and projections, where N = ranges::distance(first, last). Possible implementation Note that typical implementations use introsort. See also the imple- mentation in MSVC STL and libstdc++. struct sort_fn { template< std::random_access_iterator I, std::sentinel_for<I> S, class Comp = ranges::less, class Proj = std::identity > requires std::sortable<I, Comp, Proj> constexpr I operator()( I first, S last, Comp comp = {}, Proj proj = {} ) const { if (first == last) return first; I last_iter = ranges::next(first, last); ranges::make_heap(first, last_iter, std::ref(comp), std::ref(proj)); ranges::sort_heap(first, last_iter, std::ref(comp), std::ref(proj)); return last_iter; } template< ranges::random_access_range R, class Comp = ranges::less, class Proj = std::identity > requires std::sortable<ranges::iterator_t<R>, Comp, Proj> constexpr ranges::borrowed_iterator_t<R> operator()( R&& r, Comp comp = {}, Proj proj = {} ) const { return (*this)(ranges::begin(r), ranges::end(r), std::move(comp), std::move(proj)); } }; inline constexpr sort_fn sort{}; Notes std::sort uses std::iter_swap to swap elements, whereas ranges::sort instead uses ranges::iter_swap (which performs ADL for iter_swap, unlike std::iter_swap) Example // Run this code #include <algorithm> #include <array> #include <functional> #include <iomanip> #include <iostream> void print(auto comment, auto const& seq, char term = ' ') { for (std::cout << comment << '\n'; auto const& elem : seq) std::cout << elem << term; std::cout << '\n'; } struct Particle { std::string name; double mass; // MeV template<class Os> friend Os& operator<< (Os& os, Particle const& p) { return os << std::left << std::setw(8) << p.name << " : " << p.mass << ' '; } }; int main() { std::array s {5, 7, 4, 2, 8, 6, 1, 9, 0, 3}; namespace ranges = std::ranges; ranges::sort(s); print("Sort using the default operator<", s); ranges::sort(s, ranges::greater()); print("Sort using a standard library compare function object", s); struct { bool operator()(int a, int b) const { return a < b; } } customLess; ranges::sort(s.begin(), s.end(), customLess); print("Sort using a custom function object", s); ranges::sort(s, [](int a, int b) { return a > b; }); print("Sort using a lambda expression", s); Particle particles[] { {"Electron", 0.511}, {"Muon", 105.66}, {"Tau", 1776.86}, {"Positron", 0.511}, {"Proton", 938.27}, {"Neutron", 939.57}, }; ranges::sort(particles, {}, &Particle::name); print("\nSort by name using a projection", particles, '\n'); ranges::sort(particles, {}, &Particle::mass); print("Sort by mass using a projection", particles, '\n'); } Output: Sort using the default operator< 0 1 2 3 4 5 6 7 8 9 Sort using a standard library compare function object 9 8 7 6 5 4 3 2 1 0 Sort using a custom function object 0 1 2 3 4 5 6 7 8 9 Sort using a lambda expression 9 8 7 6 5 4 3 2 1 0 Sort by name using a projection Electron : 0.511 Muon : 105.66 Neutron : 939.57 Positron : 0.511 Proton : 938.27 Tau : 1776.86 Sort by mass using a projection Electron : 0.511 Positron : 0.511 Muon : 105.66 Proton : 938.27 Neutron : 939.57 Tau : 1776.86 See also ranges::partial_sort sorts the first N elements of a range (C++20) (niebloid) ranges::stable_sort sorts a range of elements while preserving or- der between equal (C++20) elements (niebloid) ranges::partition divides a range of elements into two groups (C++20) (niebloid) sort sorts a range into ascending order (function template) http://cppreference.com 2022.07.31 std::ranges::sort(3)
NAME | Synopsis | Parameters | Return value | Complexity | Possible implementation | Notes | Example | Output: | See also
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