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Telegram/ThirdParty/range-v3/test/view/drop.cpp

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+// Range v3 library
+//
+//  Copyright Eric Niebler 2014-present
+//
+//  Use, modification and distribution is subject to the
+//  Boost Software License, Version 1.0. (See accompanying
+//  file LICENSE_1_0.txt or copy at
+//  http://www.boost.org/LICENSE_1_0.txt)
+//
+// Project home: https://github.com/ericniebler/range-v3
+
+#include <list>
+#include <vector>
+#include <range/v3/core.hpp>
+#include <range/v3/view/chunk.hpp>
+#include <range/v3/view/drop.hpp>
+#include <range/v3/view/iota.hpp>
+#include <range/v3/view/join.hpp>
+#include <range/v3/view/reverse.hpp>
+#include <range/v3/view/take.hpp>
+#include <range/v3/view/transform.hpp>
+#include <range/v3/utility/copy.hpp>
+#include "../simple_test.hpp"
+#include "../test_utils.hpp"
+
+int main()
+{
+    using namespace ranges;
+
+    int rgi[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
+
+    {
+        auto rng0 = rgi | views::drop(6);
+        has_type<int &>(*begin(rng0));
+        CPP_assert(view_<decltype(rng0)>);
+        CPP_assert(common_range<decltype(rng0)>);
+        CPP_assert(sized_range<decltype(rng0)>);
+        CPP_assert(random_access_iterator<decltype(begin(rng0))>);
+        ::check_equal(rng0, {6, 7, 8, 9, 10});
+        CHECK(size(rng0) == 5u);
+
+        auto rng1 = rng0 | views::reverse;
+        has_type<int &>(*begin(rng1));
+        CPP_assert(view_<decltype(rng1)>);
+        CPP_assert(common_range<decltype(rng1)>);
+        CPP_assert(sized_range<decltype(rng1)>);
+        CPP_assert(random_access_iterator<decltype(begin(rng1))>);
+        ::check_equal(rng1, {10, 9, 8, 7, 6});
+    }
+
+    {
+        std::vector<int> v{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
+        auto rng2 = v | views::drop(6) | views::reverse;
+        has_type<int &>(*begin(rng2));
+        CPP_assert(view_<decltype(rng2)>);
+        CPP_assert(common_range<decltype(rng2)>);
+        CPP_assert(sized_range<decltype(rng2)>);
+        CPP_assert(random_access_iterator<decltype(begin(rng2))>);
+        ::check_equal(rng2, {10, 9, 8, 7, 6});
+    }
+
+    {
+        std::list<int> l{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
+        auto rng3 = l | views::drop(6);
+        has_type<int &>(*begin(rng3));
+        CPP_assert(view_<decltype(rng3)>);
+        CPP_assert(common_range<decltype(rng3)>);
+        CPP_assert(sized_range<decltype(rng3)>);
+        CPP_assert(bidirectional_iterator<decltype(begin(rng3))>);
+        CPP_assert(!random_access_iterator<decltype(begin(rng3))>);
+        ::check_equal(rng3, {6, 7, 8, 9, 10});
+    }
+
+    {
+        auto rng4 = views::iota(10) | views::drop(10);
+        CPP_assert(view_<decltype(rng4)>);
+        CPP_assert(!common_range<decltype(rng4)>);
+        CPP_assert(!sized_range<decltype(rng4)>);
+        static_assert(ranges::is_infinite<decltype(rng4)>::value, "");
+        auto b = ranges::begin(rng4);
+        CHECK(*b == 20);
+        CHECK(*(b+1) == 21);
+    }
+
+    {
+        auto rng5 = views::iota(10) | views::drop(10) | views::take(10) | views::reverse;
+        CPP_assert(view_<decltype(rng5)>);
+        CPP_assert(common_range<decltype(rng5)>);
+        CPP_assert(sized_range<decltype(rng5)>);
+        static_assert(!ranges::is_infinite<decltype(rng5)>::value, "");
+        ::check_equal(rng5, {29, 28, 27, 26, 25, 24, 23, 22, 21, 20});
+        CHECK(size(rng5) == 10u);
+    }
+
+    {
+        int some_ints[] = {0,1,2};
+        auto rng = make_subrange(some_ints + 0, some_ints + 1);
+        auto rng2 = views::drop(rng, 2);
+        CHECK(begin(rng2) == some_ints + 1);
+        CHECK(size(rng2) == 0u);
+    }
+
+    {
+        // Regression test for https://github.com/ericniebler/range-v3/issues/413
+        auto skips = [](std::vector<int> xs) {
+            return views::ints(0, (int)xs.size())
+                | views::transform([&](int n) {
+                    return xs | views::chunk(n + 1)
+                              | views::transform(views::drop(n))
+                              | views::join;
+                })
+                | to<std::vector<std::vector<int>>>();
+        };
+        auto skipped = skips({1,2,3,4,5,6,7,8});
+        CHECK(skipped.size() == 8u);
+        if(skipped.size() >= 8u)
+        {
+            ::check_equal(skipped[0], {1,2,3,4,5,6,7,8});
+            ::check_equal(skipped[1], {2,4,6,8});
+            ::check_equal(skipped[2], {3,6});
+            ::check_equal(skipped[3], {4,8});
+            ::check_equal(skipped[4], {5});
+            ::check_equal(skipped[5], {6});
+            ::check_equal(skipped[6], {7});
+            ::check_equal(skipped[7], {8});
+        }
+    }
+
+    {
+        static int const some_ints[] = {0,1,2,3};
+        auto rng = debug_input_view<int const>{some_ints} | views::drop(2);
+        using R = decltype(rng);
+        CPP_assert(input_range<R> && view_<R>);
+        CPP_assert(!forward_range<R>);
+        CPP_assert(same_as<int const&, range_reference_t<R>>);
+        ::check_equal(rng, {2,3});
+    }
+
+    {
+        // regression test for #728
+        auto rng1 = views::iota(1) | views::chunk(6) | views::take(3);
+        int i = 2;
+        RANGES_FOR(auto o1, rng1)
+        {
+            auto rng2 = o1 | views::drop(1);
+            ::check_equal(rng2, {i, i+1, i+2, i+3, i+4});
+            i += 6;
+        }
+    }
+
+    {
+        // regression test for #813
+        static int const some_ints[] = {0,1,2,3};
+        auto rng = some_ints | views::drop(10);
+        CHECK(empty(rng));
+    }
+
+    return test_result();
+}