new algorithms cartesian_product

Author: jesperkdab

CMakeLists.txt

@@ -68,6 +68,7 @@ if(BUILD_TESTING AND ${KDALGORITHMS_BUILD_TEST})
         src/kdalgorithms_bits/zip.h
         src/kdalgorithms_bits/tuple_utils.h
         src/kdalgorithms_bits/invoke.h
+        src/kdalgorithms_bits/cartesian_product.h
 
         tests/tst_kdalgorithms.cpp
         tests/tst_constraints.cpp

Documentation/algorithms.md

@@ -41,6 +41,7 @@ Other
 - <a href="#partitioned">partitioned</a>
 - <a href="#multi_partitioned">multi_partitioned</a>
 - <a href="#zip">zip</a>
+- <a href="#cartesian_product">product</a>
 
 
 
@@ -953,3 +954,34 @@ auto result = kdalgorithms::zip<std::deque>(v1, v2);
 ```
 
 See [boost::compine](https://www.boost.org/doc/libs/1_81_0/libs/range/doc/html/range/reference/utilities/combine.html) for similar algorithm in boost, and [std::ranges::views::zip](https://en.cppreference.com/w/cpp/ranges/zip_view) for the C++23 version.
+
+
+<a name="cartesian_product">cartesian_product</a>
+-----------------------------
+cartesian_product takes a number of containers and returns a cartesian product of the items.
+
+```
+const std::array<char, 2> x = {'A', 'B'};
+const std::vector<int> y = {1, 2, 3};
+const std::list<std::string> z = {"α", "β", "γ", "δ"};
+
+auto result = kdalgorithms::product(x, y, z);
+// result is:
+//   std::vector<std::tuple<char, int, std::string>>{
+//      {'A', 1, "α"}, {'A', 1, "β"}, {'A', 1, "γ"}, {'A', 1, "δ"}, 
+//      {'A', 2, "α"}, {'A', 2, "β"}, {'A', 2, "γ"}, {'A', 2, "δ"}, 
+//      {'A', 3, "α"}, {'A', 3, "β"}, {'A', 3, "γ"}, {'A', 3, "δ"}, 
+//      {'B', 1, "α"}, {'B', 1, "β"}, {'B', 1, "γ"}, {'B', 1, "δ"}, 
+//      {'B', 2, "α"}, {'B', 2, "β"}, {'B', 2, "γ"}, {'B', 2, "δ"},
+//      {'B', 3, "α"}, {'B', 3, "β"}, {'B', 3, "γ"}, {'B', 3, "δ"},
+//   };
+```
+
+It is also possible to specify the return type:
+```
+auto result = kdalgorithms::cartesian_product<std::deque>( x, y, z );
+// result is:
+//   std::deque<std::tuple<char, int, std::string>>{ ... }
+```
+
+See [std::cartesian_product](https://en.cppreference.com/w/cpp/ranges/cartesian_product_view)

src/kdalgorithms.h

@@ -10,6 +10,7 @@
 
 #pragma once
 
+#include "kdalgorithms_bits/cartesian_product.h"
 #include "kdalgorithms_bits/filter.h"
 #include "kdalgorithms_bits/find_if.h"
 #include "kdalgorithms_bits/generate.h"

src/kdalgorithms_bits/cartesian_product.h

@@ -0,0 +1,51 @@
+/****************************************************************************
+**
+** This file is part of KDAlgorithms
+**
+** SPDX-FileCopyrightText: 2024 Klarälvdalens Datakonsult AB, a KDAB Group company <[email protected]>
+**
+** SPDX-License-Identifier: MIT
+**
+****************************************************************************/
+
+#pragma once
+
+#include "transform.h"
+#include "tuple_utils.h"
+#include <tuple>
+#include <vector>
+
+namespace kdalgorithms {
+namespace detail {
+    template <template <typename...> class ResultContainerClass, typename Container>
+    auto cartesian_product(Container &&arg)
+    {
+        return kdalgorithms::transformed<ResultContainerClass>(
+            std::forward<Container>(arg), [](auto &&elm) { return std::make_tuple(elm); });
+    }
+
+    template <template <typename...> class ResultContainerClass, typename Container,
+              typename... REST>
+    auto cartesian_product(Container &&container, REST... args)
+    {
+        auto partialResult = cartesian_product<ResultContainerClass>(args...);
+
+        using TupleType =
+            detail::merge_tuple_types_t<ValueType<Container>, ValueType<decltype(partialResult)>>;
+        ResultContainerClass<TupleType> result;
+        for (auto &&item : container) {
+            for (auto &&partialItem : partialResult) {
+                result.push_back(std::tuple_cat(std::make_tuple(item), partialItem));
+            }
+        }
+        return result;
+    }
+} // namespace detail
+
+template <template <typename...> class ResultContainerClass = std::vector, typename... ARGS>
+auto cartesian_product(ARGS... args)
+{
+    return detail::cartesian_product<ResultContainerClass>(std::forward<ARGS>(args)...);
+}
+
+} // namespace kdalgorithms

src/kdalgorithms_bits/transform.h

@@ -11,6 +11,7 @@
 #pragma once
 
 #include "insert_wrapper.h"
+#include "read_iterator_wrapper.h"
 #include "reserve_helper.h"
 #include "shared.h"
 #include "to_function_object.h"

src/kdalgorithms_bits/tuple_utils.h

@@ -40,5 +40,16 @@ namespace detail {
                                               fn);
     }
 
+    template <typename T1, typename T2>
+    struct merge_tuple_types;
+
+    template <typename T, typename... TupleItems>
+    struct merge_tuple_types<T, std::tuple<TupleItems...>>
+    {
+        using type = std::tuple<T, TupleItems...>;
+    };
+
+    template <typename T, typename Tuple>
+    using merge_tuple_types_t = typename merge_tuple_types<T, Tuple>::type;
 } // namespace detail
 } // namespace kdalgorithms

tests/tst_kdalgorithms.cpp

@@ -15,6 +15,7 @@
 #include <QTest>
 #include <QVector>
 #include <algorithm>
+#include <array>
 #include <deque>
 #include <forward_list>
 #include <iostream>
@@ -182,6 +183,7 @@ private Q_SLOTS:
     void multi_partitioned();
     void multi_partitioned_with_function_taking_a_value();
     void sub_range();
+    void product();
 };
 
 void TestAlgorithms::copy()
@@ -2929,6 +2931,68 @@ void TestAlgorithms::sub_range()
 #endif
 }
 
+void TestAlgorithms::product()
+{
+    { // Base case
+        std::vector<int> v{1, 2, 3};
+        std::vector<std::tuple<int>> expected{{1}, {2}, {3}};
+        auto result = kdalgorithms::cartesian_product(v);
+        QCOMPARE(result, expected);
+    }
+
+    { // Two lists
+        std::vector<int> v1{1, 2};
+        std::vector<int> v2{3, 4};
+        std::vector<std::tuple<int, int>> expected{{1, 3}, {1, 4}, {2, 3}, {2, 4}};
+        auto result = kdalgorithms::cartesian_product(v1, v2);
+        QCOMPARE(result, expected);
+    }
+
+    { // Three lists
+        std::vector<int> v1{1, 2};
+        std::vector<int> v2{3, 4};
+        std::vector<int> v3{5, 6, 7};
+        std::vector<std::tuple<int, int, int>> expected{{1, 3, 5}, {1, 3, 6}, {1, 3, 7}, {1, 4, 5},
+                                                        {1, 4, 6}, {1, 4, 7}, {2, 3, 5}, {2, 3, 6},
+                                                        {2, 3, 7}, {2, 4, 5}, {2, 4, 6}, {2, 4, 7}};
+        auto result = kdalgorithms::cartesian_product(v1, v2, v3);
+        QCOMPARE(result, expected);
+    }
+
+    { // Different types
+        std::vector<int> v1{1, 2};
+        std::vector<bool> v2{true, false};
+        std::vector<std::tuple<int, bool>> expected{{1, true}, {1, false}, {2, true}, {2, false}};
+        auto result = kdalgorithms::cartesian_product(v1, v2);
+        QCOMPARE(result, expected);
+    }
+
+    { // Different container types
+        // Example from https://en.cppreference.com/w/cpp/ranges/cartesian_product_view
+        const std::array<char, 2> x = {'A', 'B'};
+        const std::vector<int> y = {1, 2, 3};
+        const std::list<std::string> z = {"α", "β", "γ", "δ"};
+
+        const auto expected = std::vector<std::tuple<char, int, std::string>>{
+            {'A', 1, "α"}, {'A', 1, "β"}, {'A', 1, "γ"}, {'A', 1, "δ"}, {'A', 2, "α"},
+            {'A', 2, "β"}, {'A', 2, "γ"}, {'A', 2, "δ"}, {'A', 3, "α"}, {'A', 3, "β"},
+            {'A', 3, "γ"}, {'A', 3, "δ"}, {'B', 1, "α"}, {'B', 1, "β"}, {'B', 1, "γ"},
+            {'B', 1, "δ"}, {'B', 2, "α"}, {'B', 2, "β"}, {'B', 2, "γ"}, {'B', 2, "δ"},
+            {'B', 3, "α"}, {'B', 3, "β"}, {'B', 3, "γ"}, {'B', 3, "δ"},
+        };
+        auto result = kdalgorithms::cartesian_product(x, y, z);
+        QCOMPARE(result, expected);
+    }
+
+    { // Result Type given
+        std::vector<int> v1{1, 2};
+        std::list<bool> v2{true, false};
+        std::deque<std::tuple<int, bool>> expected{{1, true}, {1, false}, {2, true}, {2, false}};
+        auto result = kdalgorithms::cartesian_product<std::deque>(v1, v2);
+        QCOMPARE(result, expected);
+    }
+}
+
 QTEST_MAIN(TestAlgorithms)
 
 #include "tst_kdalgorithms.moc"