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[feature] radr::counted and radr::counted_sp
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‎docs/implementation_status.md‎

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@@ -35,6 +35,7 @@ We plan to add equivalent objects for all standard library adaptors.
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| `radr::reverse` | C++20 | | `std::views::reverse` | C++20 | |
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| `radr::slice(m, n)` | C++20 | | *not yet available* | | get subrange between m and n |
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| `radr::split(pat)` | C++20 | | `std::views::split` | C++20 | |
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| *not planned* | C++20 | | `std::views::lazy_split` | C++20 | use `radr::to_single_pass | radr::split` |
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| `radr::take(n)` | C++20 | | `std::views::take` | C++20 | |
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| `radr::take_exactly(n)` | C++20 | | *not yet available* | | turns unsized into sized |
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| `radr::take_while(fn)` | C++20 | | `std::views::take_while` | C++20 | |
@@ -52,6 +53,8 @@ All range adaptors from this library are available in C++20, although `radr::as_
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| Range factories (objects) | C++XY | | Equivalent in `std::` | C++XY | Remarks |
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|-------------------------------|-------|-|-------------------------|-----------|-------------------------------------------|
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| `radr::counted(it, n)` | C++20 | | `std::views::counted` | C++20 | multi-pass version of counted |
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| `radr::counted_sp(it, n)` | C++20 | | `std::views::counted` | C++20 | single-pass version of counted |
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| `radr::empty<T>` | C++20 | | `std::views::empty` | C++20 | |
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| `radr::iota(val[, bound])` | C++20 | | `std::views::iota` | C++20 | multi-pass version of iota |
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| `radr::iota_sp(val[, bound])` | C++20 | | `std::views::iota` | C++20 | single-pass version of iota |

‎include/radr/factory/counted.hpp‎

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// -*- C++ -*-
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//===----------------------------------------------------------------------===//
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//
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// Copyright (c) 2023-2025 Hannes Hauswedell
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//
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// Licensed under the Apache License v2.0 with LLVM Exceptions.
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// See the LICENSE file for details.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#pragma once
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#include <iterator>
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#include "../rad/take.hpp"
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namespace radr
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{
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inline namespace cpo
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{
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/*!\brief Create a range from an iterator and a count.
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* \tparam It The type of \p it; required to model std::forward_iterator.
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* \param[in] it The iterator.
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* \param[in] n The count.
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* \details
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*
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* In contrast to std::views::counted, this factory always returns a multi-pass range and thus requires
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* `std::forward_iterator<It>` and not just `std::input_or_output_iterator<It>`.
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*
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* There is radr::counted_sp which is always a single-pass range and does not have this requirement.
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*
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* Unlike std::views::counted, we consider radr::counted a range factory and not a range adaptor, because
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* you cannot pipe a range into it.
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*
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* ### Safety
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*
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* Note that this function (like std::views::counted) performs no bounds-checking.
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*/
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inline constexpr auto counted = []<std::forward_iterator It>(It it, size_t const n)
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{
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/* this is a bit of a hack; the sentinels are irrelevant and also the first size parameter
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* but take_borrow will dispatch to either subborrow (for ra-iter) or else
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* (std::counted_iterator, default_sentinel) which is what we want.
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*/
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return detail::take_borrow(
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borrowing_rad{it, std::unreachable_sentinel, make_const_iterator(it), std::unreachable_sentinel, n},
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n);
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};
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/*!\brief Single-pass version of radr::counted.
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* \tparam It The type of \p it; required to model std::input_or_output_iterator.
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* \param[in,out] it The iterator.
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* \param[in] n The count.
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* \details
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*
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* This factory always returns a radr::generator, a move-only, single-pass range.
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*
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* The requirements on the iterator type are weaker than for radr::counted.
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*
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* ### Safety
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*
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* Note that this function (like std::views::counted) performs no bounds-checking.
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*/
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inline constexpr auto counted_sp = []<typename It>(It && it, size_t const n)
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{
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static_assert(std::input_or_output_iterator<std::remove_cvref_t<It>>,
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"You must pass an iterator as first argument to radr::counted_sp().");
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// Intentionally, no forwarding reference in this signature
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return [](It it, size_t const n) -> generator<std::iter_reference_t<It>, std::iter_value_t<It>>
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{
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uint64_t i = 0;
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while (i < n)
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{
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co_yield *it;
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++i;
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++it;
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}
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}(std::forward<It>(it), n);
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};
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} // namespace cpo
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} // namespace radr

‎include/radr/rad_util/borrowing_rad.hpp‎

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@@ -88,7 +88,7 @@ class borrowing_rad : public rad_interface<borrowing_rad<Iter, Sent, CIter, CSen
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}
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public:
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borrowing_rad() = default;
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constexpr borrowing_rad() = default;
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/*!\name Constructors: Iterator, Sentinel
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* \{

‎tests/unit/factory/CMakeLists.txt‎

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radr_unit_test(counted)
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radr_unit_test(empty)
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radr_unit_test(iota)
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radr_unit_test(istream)

‎tests/unit/factory/counted.cpp‎

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#include <array>
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#include <deque>
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#include <forward_list>
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#include <iterator>
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#include <list>
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#include <ranges>
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#include <vector>
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#include <gtest/gtest.h>
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#include <radr/test/gtest_helpers.hpp>
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#include <radr/factory/counted.hpp>
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#include <radr/factory/iota.hpp>
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TEST(counted, Basic)
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{
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int arr[]{1, 2, 3, 4, 5};
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auto rng = radr::counted(arr, 3);
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std::vector<int> expected{1, 2, 3};
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EXPECT_RANGE_EQ(rng, expected);
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}
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TEST(counted, EdgeCases_ZeroCount)
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{
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int arr[]{1, 2, 3};
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auto rng = radr::counted(arr, 0);
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std::vector<int> expected{};
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EXPECT_RANGE_EQ(rng, expected);
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}
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TEST(counted, EdgeCases_ExactEnd)
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{
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int arr[]{7, 8, 9, 10};
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auto rng = radr::counted(arr + 2, 2);
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std::vector<int> expected{9, 10};
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EXPECT_RANGE_EQ(rng, expected);
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}
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TEST(counted, ForwardIterator)
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{
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std::forward_list<int> flist{5, 6, 7, 8};
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auto it = flist.begin();
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std::ranges::advance(it, 1);
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auto rng = radr::counted(it, 2);
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std::vector<int> expected{6, 7};
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EXPECT_RANGE_EQ(rng, expected);
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EXPECT_TRUE(std::regular<decltype(rng)>);
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EXPECT_TRUE(radr::mp_range<decltype(rng)>);
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EXPECT_TRUE(std::ranges::sized_range<decltype(rng)>);
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EXPECT_TRUE(std::ranges::borrowed_range<decltype(rng)>);
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EXPECT_FALSE(std::ranges::bidirectional_range<decltype(rng)>);
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EXPECT_FALSE(std::ranges::random_access_range<decltype(rng)>);
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EXPECT_FALSE(std::ranges::contiguous_range<decltype(rng)>);
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EXPECT_FALSE(radr::common_range<decltype(rng)>);
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}
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TEST(counted, BidirectionalIterator)
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{
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std::list<int> lst{11, 12, 13, 14, 15};
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auto it = lst.begin();
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std::ranges::advance(it, 1);
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auto rng = radr::counted(it, 3);
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std::vector<int> expected{12, 13, 14};
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EXPECT_RANGE_EQ(rng, expected);
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EXPECT_TRUE(std::regular<decltype(rng)>);
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EXPECT_TRUE(radr::mp_range<decltype(rng)>);
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EXPECT_TRUE(std::ranges::sized_range<decltype(rng)>);
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EXPECT_TRUE(std::ranges::borrowed_range<decltype(rng)>);
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EXPECT_TRUE(std::ranges::bidirectional_range<decltype(rng)>);
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EXPECT_FALSE(std::ranges::random_access_range<decltype(rng)>);
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EXPECT_FALSE(std::ranges::contiguous_range<decltype(rng)>);
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EXPECT_FALSE(radr::common_range<decltype(rng)>);
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}
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TEST(counted, RandomAccessIterator)
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{
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std::deque<int> vec{3, 1, 4, 1, 5};
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auto rng = radr::counted(vec.begin() + 2, 2);
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std::vector<int> expected{4, 1};
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EXPECT_RANGE_EQ(rng, expected);
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EXPECT_TRUE(std::regular<decltype(rng)>);
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EXPECT_TRUE(radr::mp_range<decltype(rng)>);
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EXPECT_TRUE(std::ranges::sized_range<decltype(rng)>);
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EXPECT_TRUE(std::ranges::borrowed_range<decltype(rng)>);
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EXPECT_TRUE(std::ranges::bidirectional_range<decltype(rng)>);
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EXPECT_TRUE(std::ranges::random_access_range<decltype(rng)>);
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EXPECT_FALSE(std::ranges::contiguous_range<decltype(rng)>);
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EXPECT_TRUE(radr::common_range<decltype(rng)>);
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}
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TEST(counted, ContiguousIterator)
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{
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std::vector<int> vec{3, 1, 4, 1, 5};
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auto rng = radr::counted(vec.begin() + 2, 2);
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std::vector<int> expected{4, 1};
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EXPECT_RANGE_EQ(rng, expected);
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EXPECT_TRUE(std::regular<decltype(rng)>);
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EXPECT_TRUE(radr::mp_range<decltype(rng)>);
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EXPECT_TRUE(std::ranges::sized_range<decltype(rng)>);
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EXPECT_TRUE(std::ranges::borrowed_range<decltype(rng)>);
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EXPECT_TRUE(std::ranges::bidirectional_range<decltype(rng)>);
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EXPECT_TRUE(std::ranges::random_access_range<decltype(rng)>);
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EXPECT_TRUE(std::ranges::contiguous_range<decltype(rng)>);
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EXPECT_TRUE(radr::common_range<decltype(rng)>);
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}
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TEST(counted, Constexpr)
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{
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static constexpr std::array<int, 4> a{5, 6, 7, 8};
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constexpr auto rng = radr::counted(a.begin() + 1, 2);
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static_assert(rng.size() == 2);
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static_assert(*rng.begin() == 6);
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}
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TEST(counted, Constexpr_Zero)
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{
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static constexpr std::array<int, 1> a{1};
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constexpr auto rng = radr::counted(a.begin(), 0);
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static_assert(rng.size() == 0);
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static_assert(rng.begin() == rng.end());
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}
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//===========================================================================
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// single-pass version
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//===========================================================================
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TEST(counted_sp, Basic)
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{
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int arr[]{1, 2, 3, 4, 5};
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auto rng = radr::counted_sp(&*arr, 3);
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std::vector<int> expected{1, 2, 3};
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EXPECT_RANGE_EQ(rng, expected);
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}
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TEST(counted_sp, EdgeCases_ZeroCount)
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{
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int arr[]{1, 2, 3};
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auto rng = radr::counted_sp(&*arr, 0);
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std::vector<int> expected{};
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EXPECT_RANGE_EQ(rng, expected);
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}
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TEST(counted_sp, EdgeCases_ExactEnd)
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{
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int arr[]{7, 8, 9, 10};
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auto rng = radr::counted_sp(&*arr + 2, 2);
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std::vector<int> expected{9, 10};
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EXPECT_RANGE_EQ(rng, expected);
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}
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TEST(counted_sp, InputIterator)
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{
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auto gen = radr::iota_sp(5, 9);
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auto it = gen.begin();
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std::ranges::advance(it, 1);
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auto rng = radr::counted_sp(it, 2);
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std::vector<int> expected{6, 7};
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EXPECT_RANGE_EQ(rng, expected);
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#ifdef __cpp_lib_generator
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EXPECT_SAME_TYPE(decltype(rng), (radr::generator<int &&, int, void>));
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#else
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EXPECT_SAME_TYPE(decltype(rng), (radr::generator<int>));
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#endif
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}
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TEST(counted_sp, ForwardIterator)
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{
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std::forward_list<int> flist{5, 6, 7, 8};
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auto it = flist.begin();
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std::ranges::advance(it, 1);
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auto rng = radr::counted_sp(it, 2);
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std::vector<int> expected{6, 7};
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EXPECT_RANGE_EQ(rng, expected);
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EXPECT_SAME_TYPE(decltype(rng), (radr::generator<int &, int>));
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}
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TEST(counted_sp, BidirectionalIterator)
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{
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std::list<int> lst{11, 12, 13, 14, 15};
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auto it = lst.begin();
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std::ranges::advance(it, 1);
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auto rng = radr::counted_sp(it, 3);
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std::vector<int> expected{12, 13, 14};
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EXPECT_RANGE_EQ(rng, expected);
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EXPECT_SAME_TYPE(decltype(rng), (radr::generator<int &, int>));
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}
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TEST(counted_sp, RandomAccessIterator)
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{
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std::deque<int> vec{3, 1, 4, 1, 5};
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auto rng = radr::counted_sp(vec.begin() + 2, 2);
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std::vector<int> expected{4, 1};
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EXPECT_RANGE_EQ(rng, expected);
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EXPECT_SAME_TYPE(decltype(rng), (radr::generator<int &, int>));
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}
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TEST(counted_sp, ContiguousIterator)
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{
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std::vector<int> vec{3, 1, 4, 1, 5};
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auto rng = radr::counted_sp(vec.begin() + 2, 2);
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std::vector<int> expected{4, 1};
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EXPECT_RANGE_EQ(rng, expected);
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EXPECT_SAME_TYPE(decltype(rng), (radr::generator<int &, int>));
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}
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// generator not yet constexpr

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