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Telegram/ThirdParty/range-v3/test/algorithm/fold.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
+//
+
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include <cmath>
+#include <functional>
+
+#include <range/v3/algorithm/fold.hpp>
+#include <range/v3/algorithm/min.hpp>
+#include <range/v3/core.hpp>
+
+#include "../simple_test.hpp"
+#include "../test_iterators.hpp"
+
+struct Approx
+{
+    double value;
+    Approx(double v)
+      : value(v)
+    {}
+
+    friend bool operator==(Approx a, double d)
+    {
+        return std::fabs(a.value - d) < 0.001;
+    }
+    friend bool operator==(double d, Approx a)
+    {
+        return a == d;
+    }
+};
+
+template<class Iter, class Sent = Iter>
+void test_left()
+{
+    double da[] = {0.25, 0.75};
+    CHECK(ranges::fold_left(Iter(da), Sent(da), 1, std::plus<>()) == Approx{1.0});
+    CHECK(ranges::fold_left(Iter(da), Sent(da + 2), 1, std::plus<>()) == Approx{2.0});
+
+    CHECK(ranges::fold_left_first(Iter(da), Sent(da), ranges::min) == ranges::nullopt);
+    CHECK(ranges::fold_left_first(Iter(da), Sent(da + 2), ranges::min) ==
+          ranges::optional<Approx>(0.25));
+
+    using ranges::make_subrange;
+    CHECK(ranges::fold_left(make_subrange(Iter(da), Sent(da)), 1, std::plus<>()) ==
+          Approx{1.0});
+    CHECK(ranges::fold_left(make_subrange(Iter(da), Sent(da + 2)), 1, std::plus<>()) ==
+          Approx{2.0});
+    CHECK(ranges::fold_left_first(make_subrange(Iter(da), Sent(da)), ranges::min) ==
+          ranges::nullopt);
+    CHECK(ranges::fold_left_first(make_subrange(Iter(da), Sent(da + 2)), ranges::min) ==
+          ranges::optional<Approx>(0.25));
+}
+
+void test_right()
+{
+    double da[] = {0.25, 0.75};
+    CHECK(ranges::fold_right(da, da + 2, 1, std::plus<>()) == Approx{2.0});
+    CHECK(ranges::fold_right(da, 1, std::plus<>()) == Approx{2.0});
+
+    // f(0.25, f(0.75, 1))
+    CHECK(ranges::fold_right(da, da + 2, 1, std::minus<>()) == Approx{0.5});
+    CHECK(ranges::fold_right(da, 1, std::minus<>()) == Approx{0.5});
+
+    int xs[] = {1, 2, 3};
+    auto concat = [](int i, std::string s) { return s + std::to_string(i); };
+    CHECK(ranges::fold_right(xs, xs + 2, std::string(), concat) == "21");
+    CHECK(ranges::fold_right(xs, std::string(), concat) == "321");
+}
+
+int main()
+{
+    test_left<InputIterator<const double *>>();
+    test_left<ForwardIterator<const double *>>();
+    test_left<BidirectionalIterator<const double *>>();
+    test_left<RandomAccessIterator<const double *>>();
+    test_left<const double *>();
+
+    test_left<InputIterator<const double *>, Sentinel<const double *>>();
+    test_left<ForwardIterator<const double *>, Sentinel<const double *>>();
+    test_left<BidirectionalIterator<const double *>, Sentinel<const double *>>();
+    test_left<RandomAccessIterator<const double *>, Sentinel<const double *>>();
+
+    test_right();
+
+    return ::test_result();
+}