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//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
// REQUIRES: std-at-least-c++23
// <ranges>
// friend constexpr void iter_swap(const iterator& x, const iterator& y);
#include <ranges>
#include <algorithm>
#include <array>
#include <cassert>
#include <span>
#include <string>
#include <string_view>
#include <type_traits>
#include <utility>
#include <vector>
template <class I>
concept CanIterSwap = requires(I i) { iter_swap(i); };
enum class SwapKind { no_swap, with_same_type, with_different_type };
enum class IterKind { inner_view, pattern };
template <std::forward_iterator Iter, IterKind Kind>
class IterSwapTrackingIterator {
public:
using value_type = std::iter_value_t<Iter>;
using difference_type = std::iter_difference_t<Iter>;
constexpr Iter get_iter() const { return iter_; }
constexpr SwapKind* get_flag() const { return flag_; }
IterSwapTrackingIterator() = default;
constexpr explicit IterSwapTrackingIterator(Iter iter, SwapKind* flag = nullptr)
: iter_(std::move(iter)), flag_(flag) {}
constexpr IterSwapTrackingIterator& operator++() {
++iter_;
return *this;
}
constexpr IterSwapTrackingIterator operator++(int) {
auto tmp = *this;
++*this;
return tmp;
}
constexpr decltype(auto) operator*() const { return *iter_; }
constexpr bool operator==(const IterSwapTrackingIterator& other) const { return iter_ == other.iter_; }
friend constexpr decltype(auto) iter_swap(const IterSwapTrackingIterator& lhs, const IterSwapTrackingIterator& rhs) {
assert(lhs.flag_ != nullptr && rhs.flag_ != nullptr);
*lhs.flag_ = *rhs.flag_ = SwapKind::with_same_type;
return std::ranges::iter_swap(lhs.iter_, rhs.iter_);
}
template <std::indirectly_swappable<Iter> OtherIter, IterKind OtherKind>
friend constexpr decltype(auto)
iter_swap(const IterSwapTrackingIterator& lhs, const IterSwapTrackingIterator<OtherIter, OtherKind>& rhs) {
assert(lhs.flag_ != nullptr && rhs.get_flag() != nullptr);
*lhs.flag_ = *rhs.get_flag() = SwapKind::with_different_type;
return std::ranges::iter_swap(lhs.iter_, rhs.get_iter());
}
private:
Iter iter_ = Iter();
SwapKind* flag_ = nullptr;
};
static_assert(std::forward_iterator<IterSwapTrackingIterator<int*, IterKind::inner_view>> &&
!std::bidirectional_iterator<IterSwapTrackingIterator<int*, IterKind::inner_view>>);
constexpr bool test() {
{ // Test common usage
using V = std::vector<std::string>;
using Pattern = std::string;
using JWV = std::ranges::join_with_view<std::ranges::owning_view<V>, std::ranges::owning_view<Pattern>>;
using namespace std::string_view_literals;
JWV jwv(V{"std", "ranges", "views", "join_with_view"}, Pattern{":: "});
assert(std::ranges::equal(jwv, "std:: ranges:: views:: join_with_view"sv));
auto it = jwv.begin();
iter_swap(it, std::ranges::next(it, 2)); // Swap elements of the same inner range.
assert(std::ranges::equal(jwv, "dts:: ranges:: views:: join_with_view"sv));
std::ranges::advance(it, 3);
iter_swap(std::as_const(it), std::ranges::next(it, 2)); // Swap elements of the pattern.
assert(std::ranges::equal(jwv, "dts ::ranges ::views ::join_with_view"sv));
std::ranges::advance(it, 3);
const auto it2 = jwv.begin();
iter_swap(std::as_const(it), it2); // Swap elements of different inner ranges.
assert(std::ranges::equal(jwv, "rts ::danges ::views ::join_with_view"sv));
std::ranges::advance(it, 6);
iter_swap(std::as_const(it), it2); // Swap element from inner range with element from the pattern.
assert(std::ranges::equal(jwv, " tsr::dangesr::viewsr::join_with_view"sv));
static_assert(std::is_void_v<decltype(iter_swap(it, it))>);
static_assert(std::is_void_v<decltype(iter_swap(it2, it2))>);
static_assert(!CanIterSwap<std::ranges::iterator_t<const JWV>>);
static_assert(!CanIterSwap<const std::ranges::iterator_t<const JWV>>);
}
{ // Make sure `iter_swap` calls underlying's iterator `iter_swap` (not `ranges::swap(*i1, *i2)`).
using Inner = std::vector<int>;
using InnerTrackingIter = IterSwapTrackingIterator<Inner::iterator, IterKind::inner_view>;
using TrackingInner = std::ranges::subrange<InnerTrackingIter>;
using Pattern = std::array<int, 2>;
using PatternTrackingIter = IterSwapTrackingIterator<Pattern::iterator, IterKind::pattern>;
using TrackingPattern = std::ranges::subrange<PatternTrackingIter>;
using JWV = std::ranges::join_with_view<std::span<TrackingInner>, TrackingPattern>;
std::array<Inner, 3> v{{{1, 2, 3}, {4, 5}}};
Pattern pat{-1, -2};
SwapKind v_swap_kind = SwapKind::no_swap;
std::array<TrackingInner, 2> tracking_v{
TrackingInner(InnerTrackingIter(v[0].begin(), &v_swap_kind), InnerTrackingIter(v[0].end())),
TrackingInner(InnerTrackingIter(v[1].begin(), &v_swap_kind), InnerTrackingIter(v[1].end()))};
SwapKind pat_swap_kind = SwapKind::no_swap;
TrackingPattern tracking_pat(PatternTrackingIter(pat.begin(), &pat_swap_kind), PatternTrackingIter(pat.end()));
JWV jwv(tracking_v, tracking_pat);
auto it1 = jwv.begin();
auto it2 = std::ranges::next(it1);
// Test calling `iter_swap` when both `it1` and `it2` point to elements of `v`.
assert(v_swap_kind == SwapKind::no_swap);
iter_swap(it1, it2);
assert(*it1 == 2 && *it2 == 1);
assert(v_swap_kind == SwapKind::with_same_type && pat_swap_kind == SwapKind::no_swap);
// Test calling `iter_swap` when `it1` points to element of `v` and `it2` points to element of `pat`.
std::ranges::advance(it2, 2);
v_swap_kind = SwapKind::no_swap;
assert(pat_swap_kind == SwapKind::no_swap);
iter_swap(it1, it2);
assert(*it1 == -1 && *it2 == 2);
assert(v_swap_kind == SwapKind::with_different_type && pat_swap_kind == SwapKind::with_different_type);
// Test calling `iter_swap` when `it1` and `it2` point to elements of `pat`.
std::ranges::advance(it1, 4);
v_swap_kind = pat_swap_kind = SwapKind::no_swap;
iter_swap(it1, it2);
assert(*it1 == 2 && *it2 == -2);
assert(v_swap_kind == SwapKind::no_swap && pat_swap_kind == SwapKind::with_same_type);
// Test calling `iter_swap` when `it1` points to element of `pat` and `it2` points to element of `v`.
std::ranges::advance(it2, 3);
v_swap_kind = pat_swap_kind = SwapKind::no_swap;
iter_swap(it1, it2);
assert(*it1 == 5 && *it2 == 2);
assert(v_swap_kind == SwapKind::with_different_type && pat_swap_kind == SwapKind::with_different_type);
}
{ // InnerIter and PatternIter don't model indirectly swappable
using JWV = std::ranges::join_with_view<std::span<std::string>, std::string_view>;
static_assert(!CanIterSwap<std::ranges::iterator_t<JWV>>);
static_assert(!CanIterSwap<const std::ranges::iterator_t<JWV>>);
static_assert(!CanIterSwap<std::ranges::iterator_t<const JWV>>);
static_assert(!CanIterSwap<const std::ranges::iterator_t<const JWV>>);
}
return true;
}
int main(int, char**) {
test();
static_assert(test());
return 0;
}
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