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This is a follow-up question for A recursive_transform_reduce Template Function with Unwrap Level Implementation in C++. To fix the issue mentioned in G. Sliepen's answer, I updated the test cases and recursive_transform_reduce itself. Please check them again. If there is anything I missed, please let me know.

Test Cases

  • Nested std::vector Test Case:

    //  test case with nested std::vector
    auto test_vectors_1 = n_dim_container_generator<1, int, std::vector>(1, 3);
    std::vector<decltype(test_vectors_1)> test_vectors_2 = {test_vectors_1, test_vectors_1};
    M_Assert(recursive_transform_reduce<2>(test_vectors_2, 1) == 7,
            "Test case with nested std::vector failed");
    
  • Nested std::array Test Case:

    //  test case with nested std::array
    std::array<int, 3> test_array_1 = {1, 1, 1};
    std::array<decltype(test_array_1), 2> test_array_2 = {test_array_1, test_array_1};
    M_Assert(recursive_transform_reduce<2>(test_array_2, 1) == 7,
            "Test case with nested std::vector failed");
    
  • Nested std::deque Test Case:

    auto test_deque_1 = n_dim_container_generator<1, int, std::deque>(1, 3);
    std::deque<decltype(test_deque_1)> test_deque_2 = {test_deque_1, test_deque_1};
    M_Assert(recursive_transform_reduce<2>(test_deque_2, 1) == 7,
            "Test case with nested std::deque failed");
    
  • Nested std::list Test Case:

    //  test case with nested std::list
    auto test_list_1 = n_dim_container_generator<1, int, std::list>(1, 3);
    std::list<decltype(test_list_1)> test_list_2 = {test_list_1, test_list_1};
    M_Assert(recursive_transform_reduce<2>(test_list_2, 1) == 7,
            "Test case with nested std::list failed");
    

The experimental implementation

  • recursive_transform_reduce Template Function

    //  recursive_transform_reduce template function implementation
    template<std::size_t unwrap_level, class Input, class T, class UnaryOp = std::identity, class BinaryOp = std::plus<T>>
    requires(recursive_invocable<unwrap_level, UnaryOp, Input>)
    constexpr auto recursive_transform_reduce(const Input& input, T init = {}, const UnaryOp& unary_op = {}, const BinaryOp& binop = std::plus<T>())
    {
        if constexpr (unwrap_level > 0)
        {
            return std::transform_reduce(std::ranges::begin(input), std::ranges::end(input), init, binop, [&](auto& element) {
                return recursive_transform_reduce<unwrap_level - 1>(element, T{}, unary_op, binop);
            });
        }
        else
        {
            return std::invoke(unary_op, input);
        }
    }
    
    //  recursive_transform_reduce template function implementation with execution policy
    template<std::size_t unwrap_level, class ExecutionPolicy, class Input, class T, class UnaryOp = std::identity, class BinaryOp = std::plus<T>>
    requires(recursive_invocable<unwrap_level, UnaryOp, Input>&&
             std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>>)
    constexpr auto recursive_transform_reduce(ExecutionPolicy execution_policy, const Input& input, T init = {}, const UnaryOp& unary_op = {}, const BinaryOp& binop = std::plus<T>())
    {
        if constexpr (unwrap_level > 0)
        {
            return std::transform_reduce(
                execution_policy,
                std::ranges::begin(input),
                std::ranges::end(input),
                init,
                binop,
                [&](auto& element) {
                return recursive_transform_reduce<unwrap_level - 1>(execution_policy, element, T{}, unary_op, binop);
            });
        }
        else
        {
            return std::invoke(unary_op, input);
        }
    }
    

Full Testing Code

The full testing code:

//  An Updated recursive_transform_reduce Template Function with Unwrap Level Implementation in C++

#include <algorithm>
#include <array>
#include <cassert>
#include <chrono>
#include <concepts>
#include <deque>
#include <execution>
#include <exception>
//#include <experimental/ranges/algorithm>
#include <experimental/array>
#include <functional>
#include <iostream>
#include <iterator>
#include <list>
#include <ranges>
#include <string>
#include <utility>
#include <vector>

//  is_reservable concept
template<class T>
concept is_reservable = requires(T input)
{
    input.reserve(1);
};

//  is_sized concept, https://codereview.stackexchange.com/a/283581/231235
template<class T>
concept is_sized = requires(T x)
{
    std::size(x);
};

template<typename T>
concept is_summable = requires(T x) { x + x; };

//  recursive_unwrap_type_t struct implementation
template<std::size_t, typename, typename...>
struct recursive_unwrap_type { };

template<class...Ts1, template<class...>class Container1, typename... Ts>
struct recursive_unwrap_type<1, Container1<Ts1...>, Ts...>
{
    using type = std::ranges::range_value_t<Container1<Ts1...>>;
};

template<std::size_t unwrap_level, class...Ts1, template<class...>class Container1, typename... Ts>
requires (  std::ranges::input_range<Container1<Ts1...>> &&
            requires { typename recursive_unwrap_type<
                                    unwrap_level - 1,
                                    std::ranges::range_value_t<Container1<Ts1...>>,
                                    std::ranges::range_value_t<Ts>...>::type; })                //  The rest arguments are ranges
struct recursive_unwrap_type<unwrap_level, Container1<Ts1...>, Ts...>
{
    using type = typename recursive_unwrap_type<
        unwrap_level - 1,
        std::ranges::range_value_t<Container1<Ts1...>>
        >::type;
};

template<std::size_t unwrap_level, typename T1, typename... Ts>
using recursive_unwrap_type_t = typename recursive_unwrap_type<unwrap_level, T1, Ts...>::type;

//  recursive_variadic_invoke_result_t implementation
template<std::size_t, typename, typename, typename...>
struct recursive_variadic_invoke_result { };

template<typename F, class...Ts1, template<class...>class Container1, typename... Ts>
struct recursive_variadic_invoke_result<1, F, Container1<Ts1...>, Ts...>
{
    using type = Container1<std::invoke_result_t<F,
        std::ranges::range_value_t<Container1<Ts1...>>,
        std::ranges::range_value_t<Ts>...>>;
};

template<std::size_t unwrap_level, typename F, class...Ts1, template<class...>class Container1, typename... Ts>
requires (  std::ranges::input_range<Container1<Ts1...>> &&
            requires { typename recursive_variadic_invoke_result<
                                    unwrap_level - 1,
                                    F,
                                    std::ranges::range_value_t<Container1<Ts1...>>,
                                    std::ranges::range_value_t<Ts>...>::type; })                //  The rest arguments are ranges
struct recursive_variadic_invoke_result<unwrap_level, F, Container1<Ts1...>, Ts...>
{
    using type = Container1<
        typename recursive_variadic_invoke_result<
        unwrap_level - 1,
        F,
        std::ranges::range_value_t<Container1<Ts1...>>,
        std::ranges::range_value_t<Ts>...
        >::type>;
};

template<std::size_t unwrap_level, typename F, typename T1, typename... Ts>
using recursive_variadic_invoke_result_t = typename recursive_variadic_invoke_result<unwrap_level, F, T1, Ts...>::type;

//  recursive_array_invoke_result implementation
template<std::size_t, typename, typename, typename...>
struct recursive_array_invoke_result { };

template<   typename F, 
            template<class, std::size_t> class Container,
            typename T,
            std::size_t N>
struct recursive_array_invoke_result<1, F, Container<T, N>>
{
    using type = Container<
        std::invoke_result_t<F, std::ranges::range_value_t<Container<T, N>>>,
        N>;
};

template<   std::size_t unwrap_level,
            typename F, 
            template<class, std::size_t> class Container,
            typename T,
            std::size_t N>
requires (  std::ranges::input_range<Container<T, N>> &&
            requires { typename recursive_array_invoke_result<
                                    unwrap_level - 1,
                                    F,
                                    std::ranges::range_value_t<Container<T, N>>>::type; })                //  The rest arguments are ranges
struct recursive_array_invoke_result<unwrap_level, F, Container<T, N>>
{
    using type = Container<
        typename recursive_array_invoke_result<
        unwrap_level - 1,
        F,
        std::ranges::range_value_t<Container<T, N>>
        >::type, N>;
};

template<   std::size_t unwrap_level,
            typename F,
            template<class, std::size_t> class Container,
            typename T,
            std::size_t N>
using recursive_array_invoke_result_t = typename recursive_array_invoke_result<unwrap_level, F, Container<T, N>>::type;

//  recursive_array_unwrap_type struct implementation, https://stackoverflow.com/a/76347485/6667035
template<std::size_t, typename>
struct recursive_array_unwrap_type { };

template<template<class, std::size_t> class Container,
              typename T,
              std::size_t N>
struct recursive_array_unwrap_type<1, Container<T, N>>
{
    using type = std::ranges::range_value_t<Container<T, N>>;
};

template<std::size_t unwrap_level, template<class, std::size_t> class Container,
              typename T,
              std::size_t N>
requires (  std::ranges::input_range<Container<T, N>> &&
            requires { typename recursive_array_unwrap_type<
                                    unwrap_level - 1,
                                    std::ranges::range_value_t<Container<T, N>>>::type; })                //  The rest arguments are ranges
struct recursive_array_unwrap_type<unwrap_level, Container<T, N>>
{
    using type = typename recursive_array_unwrap_type<
        unwrap_level - 1,
        std::ranges::range_value_t<Container<T, N>>
        >::type;
};

template<std::size_t unwrap_level, class Container>
using recursive_array_unwrap_type_t = typename recursive_array_unwrap_type<unwrap_level, Container>::type;

//  https://codereview.stackexchange.com/a/253039/231235
template<std::size_t dim, class T, template<class...> class Container = std::vector>
constexpr auto n_dim_container_generator(T input, std::size_t times)
{
    if constexpr (dim == 0)
    {
        return input;
    }
    else
    {
        return Container(times, n_dim_container_generator<dim - 1, T, Container>(input, times));
    }
}

template<std::size_t dim, std::size_t times, class T>
constexpr auto n_dim_array_generator(T input)
{
    if constexpr (dim == 0)
    {
        return input;
    }
    else
    {
        std::array<decltype(n_dim_array_generator<dim - 1, times>(input)), times> output;
        for (size_t i = 0; i < times; i++)
        {
            output[i] = n_dim_array_generator<dim - 1, times>(input);
        }
        return output;
    }
}

//  recursive_depth function implementation
template<typename T>
constexpr std::size_t recursive_depth()
{
    return std::size_t{0};
}

template<std::ranges::input_range Range>
constexpr std::size_t recursive_depth()
{
    return recursive_depth<std::ranges::range_value_t<Range>>() + std::size_t{1};
}

//  recursive_depth function implementation with target type
template<typename T_Base, typename T>
constexpr std::size_t recursive_depth()
{
    return std::size_t{0};
}

template<typename T_Base, std::ranges::input_range Range>
requires (!std::same_as<Range, T_Base>)
constexpr std::size_t recursive_depth()
{
    return recursive_depth<T_Base, std::ranges::range_value_t<Range>>() + std::size_t{1};
}

//  is_recursive_invocable template function implementation
template<std::size_t unwrap_level, class F, class... T>
requires(unwrap_level <= recursive_depth<T...>())
static constexpr bool is_recursive_invocable()
{
    if constexpr (unwrap_level == 0) {
        return std::invocable<F, T...>;
    } else {
        return is_recursive_invocable<
                    unwrap_level - 1,
                    F,
                    std::ranges::range_value_t<T>...>();
    }
}

//  recursive_invocable concept
template<std::size_t unwrap_level, class F, class... T>
concept recursive_invocable =
        is_recursive_invocable<unwrap_level, F, T...>();

//  is_recursive_project_invocable template function implementation
template<std::size_t unwrap_level, class Proj, class F, class... T>
requires(unwrap_level <= recursive_depth<T...>() &&
         recursive_invocable<unwrap_level, Proj, T...>)
static constexpr bool is_recursive_project_invocable()
{
    if constexpr (unwrap_level == 0) {
        return std::invocable<F, std::invoke_result_t<Proj, T...>>;
    } else {
        return is_recursive_project_invocable<
                    unwrap_level - 1,
                    Proj,
                    F,
                    std::ranges::range_value_t<T>...>();
    }
}

//  recursive_project_invocable concept
template<class F, std::size_t unwrap_level, class Proj, class... T>
concept recursive_projected_invocable =
        is_recursive_project_invocable<unwrap_level, Proj, F, T...>();

/*  recursive_all_of template function implementation with unwrap level
*/
template<std::size_t unwrap_level, class T, class Proj = std::identity, 
         recursive_projected_invocable<unwrap_level, Proj, T> UnaryPredicate>
constexpr auto recursive_all_of(T&& value, UnaryPredicate&& p, Proj&& proj = {}) {
    if constexpr (unwrap_level > 0)
    {
        return std::ranges::all_of(value, [&](auto&& element) {
            return recursive_all_of<unwrap_level - 1>(element, p, proj);
        });
    }
    else
    {
        return std::invoke(p, std::invoke(proj, value));
    }
}

/*  recursive_find template function implementation with unwrap level
*/
template<std::size_t unwrap_level, class R, class T, class Proj = std::identity>
requires(recursive_invocable<unwrap_level, Proj, R>)
constexpr auto recursive_find(R&& range, T&& target, Proj&& proj = {})
{
    if constexpr (unwrap_level > 0)
    {
        return std::ranges::find_if(range, [&](auto& element) {
            return recursive_find<unwrap_level - 1>(element, target, proj);
        }) != std::ranges::end(range);
    }
    else
    {
        return range == std::invoke(proj, target);
    }
}

template<std::size_t unwrap_level, class ExecutionPolicy, class R, class T, class Proj = std::identity>
requires(recursive_invocable<unwrap_level, Proj, R>&&
         std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>>)
constexpr auto recursive_find(ExecutionPolicy execution_policy, R&& range, T&& target, Proj&& proj = {})
{
    if constexpr (unwrap_level > 0)
    {
        return std::find_if(execution_policy,
                    std::ranges::begin(range),
                    std::ranges::end(range),
                    [&](auto& element) {
            return recursive_find<unwrap_level - 1>(execution_policy, element, target, proj);
        }) != std::ranges::end(range);
    }
    else
    {
        return range == std::invoke(proj, target);
    }
}

/*  recursive_find_if template function implementation with unwrap level
*/
template<std::size_t unwrap_level, class T, class Proj = std::identity, 
         recursive_projected_invocable<unwrap_level, Proj, T> UnaryPredicate>
constexpr auto recursive_find_if(T&& value, UnaryPredicate&& p, Proj&& proj = {}) {
    if constexpr (unwrap_level > 0)
    {
        return std::ranges::find_if(value, [&](auto& element) {
            return recursive_find_if<unwrap_level - 1>(element, p, proj);
        }) != std::ranges::end(value);
    }
    else
    {
        return std::invoke(p, std::invoke(proj, value));
    }
}

/*  recursive_find_if_not template function implementation with unwrap level
*/
template<std::size_t unwrap_level, class T, class Proj = std::identity, 
         recursive_projected_invocable<unwrap_level, Proj, T> UnaryPredicate>
constexpr auto recursive_find_if_not(T&& value, UnaryPredicate&& p, Proj&& proj = {}) {
    if constexpr (unwrap_level > 0)
    {
        return std::ranges::find_if(value, [&](auto& element) {
            return recursive_find_if_not<unwrap_level - 1>(element, p, proj);
        }) != std::ranges::end(value);
    }
    else
    {
        return !std::invoke(p, std::invoke(proj, value));
    }
}

//  recursive_any_of template function implementation with unwrap level
template<std::size_t unwrap_level, class T, class Proj = std::identity, 
         recursive_projected_invocable<unwrap_level, Proj, T> UnaryPredicate>
constexpr auto recursive_any_of(T&& value, UnaryPredicate&& p, Proj&& proj = {})
{
    return recursive_find_if<unwrap_level>(value, p, proj);
}

//  recursive_none_of template function implementation with unwrap level
template<std::size_t unwrap_level, class T, class Proj = std::identity, 
         recursive_projected_invocable<unwrap_level, Proj, T> UnaryPredicate>
constexpr auto recursive_none_of(T&& value, UnaryPredicate&& p, Proj&& proj = {})
{
    return !recursive_any_of<unwrap_level>(value, p, proj);
}

template<std::ranges::input_range T>
constexpr auto recursive_print(const T& input, const int level = 0)
{
    T output = input;
    std::cout << std::string(level, ' ') << "Level " << level << ":" << std::endl;
    std::transform(std::ranges::cbegin(input), std::ranges::cend(input), output.begin(), 
        [level](auto&& x)
        {
            std::cout << std::string(level, ' ') << x << std::endl;
            return x;
        }
    );
    return output;
}

template<std::ranges::input_range T>
requires (std::ranges::input_range<std::ranges::range_value_t<T>>)
constexpr T recursive_print(const T& input, const int level = 0)
{
    T output = input;
    std::cout << std::string(level, ' ') << "Level " << level << ":" << std::endl;
    std::ranges::transform(std::ranges::cbegin(input), std::ranges::cend(input), std::ranges::begin(output),
        [level](auto&& element)
        {
            return recursive_print(element, level + 1);
        }
    );
    return output;
}

//  recursive_transform_reduce template function implementation
template<std::size_t unwrap_level, class Input, class T, class UnaryOp = std::identity, class BinaryOp = std::plus<T>>
requires(recursive_invocable<unwrap_level, UnaryOp, Input>)
constexpr auto recursive_transform_reduce(const Input& input, T init = {}, const UnaryOp& unary_op = {}, const BinaryOp& binop = std::plus<T>())
{
    if constexpr (unwrap_level > 0)
    {
        return std::transform_reduce(std::ranges::begin(input), std::ranges::end(input), init, binop, [&](auto& element) {
            return recursive_transform_reduce<unwrap_level - 1>(element, T{}, unary_op, binop);
        });
    }
    else
    {
        return std::invoke(unary_op, input);
    }
}

//  recursive_transform_reduce template function implementation with execution policy
template<std::size_t unwrap_level, class ExecutionPolicy, class Input, class T, class UnaryOp = std::identity, class BinaryOp = std::plus<T>>
requires(recursive_invocable<unwrap_level, UnaryOp, Input>&&
         std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>>)
constexpr auto recursive_transform_reduce(ExecutionPolicy execution_policy, const Input& input, T init = {}, const UnaryOp& unary_op = {}, const BinaryOp& binop = std::plus<T>())
{
    if constexpr (unwrap_level > 0)
    {
        return std::transform_reduce(
            execution_policy,
            std::ranges::begin(input),
            std::ranges::end(input),
            init,
            binop,
            [&](auto& element) {
            return recursive_transform_reduce<unwrap_level - 1>(execution_policy, element, T{}, unary_op, binop);
        });
    }
    else
    {
        return std::invoke(unary_op, input);
    }
}

//  recursive_size template function implementation
template<class T> requires (!std::ranges::range<T>)
constexpr auto recursive_size(const T& input)
{
    return std::size_t{1};
}

template<std::ranges::range Range> requires (!(std::ranges::input_range<std::ranges::range_value_t<Range>>))
constexpr auto recursive_size(const Range& input)
{
    return std::ranges::size(input);
}

template<std::ranges::range Range> requires (std::ranges::input_range<std::ranges::range_value_t<Range>>)
constexpr auto recursive_size(const Range& input)
{
    return std::transform_reduce(std::ranges::begin(input), std::ranges::end(input), std::size_t{}, std::plus<std::size_t>(), [](auto& element) {
        return recursive_size(element);
        });
}

template<typename T>
concept is_recursive_sizeable = requires(T x)
{
    recursive_size(x);
};

//  Copy from https://stackoverflow.com/a/37264642/6667035
#ifndef NDEBUG
#   define M_Assert(Expr, Msg) \
    __M_Assert(#Expr, Expr, __FILE__, __LINE__, Msg)
#else
#   define M_Assert(Expr, Msg) ;
#endif

void __M_Assert(const char* expr_str, bool expr, const char* file, int line, const char* msg)
{
    if (!expr)
    {
        std::cerr << "Assert failed:\t" << msg << "\n"
            << "Expected:\t" << expr_str << "\n"
            << "Source:\t\t" << file << ", line " << line << "\n";
        abort();
    }
}

void recursive_transform_reduce_tests()
{
    auto test_vectors_1 = n_dim_container_generator<1, int, std::vector>(1, 3);
    //  basic usage case
    M_Assert(recursive_transform_reduce<1>(test_vectors_1, 0) == 3, "Basic usage case failed");

    //  basic usage case with execution policy
    M_Assert(recursive_transform_reduce<1>(std::execution::par, test_vectors_1, 0) == 3,
        "Basic usage case with execution policy failed");

    //  test case with unary operation
    M_Assert(recursive_transform_reduce<1>(
        test_vectors_1,
        0,
        [&](auto&& element) { return element + 1; }) == 6,
        "Test case with unary operation failed");

    //  test case with unary operation, execution policy
    M_Assert(recursive_transform_reduce<1>(
        std::execution::par,
        test_vectors_1,
        0,
        [&](auto&& element) { return element + 1; }) == 6,
        "Test case with unary operation, execution policy failed");

    //  test case with unary operation and binary operation
    M_Assert(recursive_transform_reduce<1>(
        test_vectors_1,
        1,
        [&](auto&& element) { return element + 1; },
        [&](auto&& element1, auto&& element2) { return element1 * element2; }) == 8,
        "Test case with unary operation and binary operation failed");

    //  test case with unary operation, binary operation and execution policy
    M_Assert(recursive_transform_reduce<1>(
        std::execution::par,
        test_vectors_1,
        1,
        [&](auto&& element) { return element + 1; },
        [&](auto&& element1, auto&& element2) { return element1 * element2; }) == 8,
        "Test case with unary operation, binary operation and execution policy failed");

    auto test_string_vector_1 = n_dim_container_generator<1, std::string, std::vector>("1", 3);
    //  test case with std::string
    M_Assert(recursive_transform_reduce<1>(test_string_vector_1, std::string("")) == "111",
        "Test case with std::string failed");

    //  test case with std::string, execution policy
    M_Assert(recursive_transform_reduce<1>(
        std::execution::par,
        test_string_vector_1, std::string("")) == "111",
        "Test case with std::string, execution policy failed");

    //  test case with std::string, unary operation
    M_Assert(recursive_transform_reduce<1>(
        test_string_vector_1,
        std::string(""),
        [&](auto&& element) { return element + "2";}) == "121212",
        "Test case with std::string, unary operation failed");

    //  test case with std::string, unary operation, execution policy
    M_Assert(recursive_transform_reduce<1>(
        std::execution::par,
        test_string_vector_1,
        std::string(""),
        [&](auto&& element) { return element + "2";}) == "121212",
        "Test case with std::string, unary operation, execution policy failed");

    //  test case with nested std::vector
    std::vector<decltype(test_vectors_1)> test_vectors_2 = {test_vectors_1, test_vectors_1};
    M_Assert(recursive_transform_reduce<2>(test_vectors_2, 1) == 7,
        "Test case with nested std::vector failed");

    //  test case with nested std::vector, execution policy
    M_Assert(recursive_transform_reduce<2>(std::execution::par, test_vectors_2, 1) == 7,
        "Test case with nested std::vector, execution policy failed");

    //  test case with nested std::array
    std::array<int, 3> test_array_1 = {1, 1, 1};
    std::array<decltype(test_array_1), 2> test_array_2 = {test_array_1, test_array_1};
    M_Assert(recursive_transform_reduce<2>(test_array_2, 1) == 7,
        "Test case with nested std::vector failed");

    //  test case with nested std::array, execution policy
    M_Assert(recursive_transform_reduce<2>(std::execution::par, test_array_2, 1) == 7,
        "Test case with nested std::vector, execution policy failed");

    //  test case with nested std::deque
    auto test_deque_1 = n_dim_container_generator<1, int, std::deque>(1, 3);
    std::deque<decltype(test_deque_1)> test_deque_2 = {test_deque_1, test_deque_1};
    M_Assert(recursive_transform_reduce<2>(test_deque_2, 1) == 7,
        "Test case with nested std::deque failed");
    
    //  test case with nested std::deque, execution policy
    M_Assert(recursive_transform_reduce<2>(std::execution::par, test_deque_2, 1) == 7,
        "Test case with nested std::deque, execution policy failed");

    //  test case with nested std::list
    auto test_list_1 = n_dim_container_generator<1, int, std::list>(1, 3);
    std::list<decltype(test_list_1)> test_list_2 = {test_list_1, test_list_1};
    M_Assert(recursive_transform_reduce<2>(test_list_2, 1) == 7,
        "Test case with nested std::list failed");

    //  test case with nested std::list, execution policy
    M_Assert(recursive_transform_reduce<2>(std::execution::par, test_list_2, 1) == 7,
        "Test case with nested std::list, execution policy failed");

    std::cout << "All tests passed!\n";

    return;
}

int main()
{
    auto start = std::chrono::system_clock::now();
    recursive_transform_reduce_tests();
    auto end = std::chrono::system_clock::now();
    std::chrono::duration<double> elapsed_seconds = end - start;
    std::time_t end_time = std::chrono::system_clock::to_time_t(end);
    std::cout << "Computation finished at " << std::ctime(&end_time) << "elapsed time: " << elapsed_seconds.count() << '\n';
    return EXIT_SUCCESS;
}

The output of the test code above:

All tests passed!
Computation finished at Wed Mar  6 01:28:55 2024
elapsed time: 0.00140866

Godbolt link is here.

All suggestions are welcome.

The summary information:

\$\endgroup\$
8
  • \$\begingroup\$ It’s been a long time since I answered one of these. I don’t want to discourage you, but you’ve asked about so many iterations of this project, and I don’t feel I have a lot more to say that I haven’t already said. \$\endgroup\$
    – Davislor
    Mar 4 at 4:38
  • \$\begingroup\$ Specifically, 1: I much prefer to have the templates detect when the recursion has gotten to objects of the same type as the argument to the reduction function, and eliminate the unwrap level parameter. You would only need it in some really weird corner cases such as a tree of iterable links to trees and a reduction function on trees. In all normal cases, the user wants the implementation that’s simpler, error-prone and also has no runtime overhead. \$\endgroup\$
    – Davislor
    Mar 4 at 4:44
  • \$\begingroup\$ 2: I’d recommend you adopt more of the conventions and terminology of functional programming, such as traversal and folding. There’s been a lot of CS research into them. \$\endgroup\$
    – Davislor
    Mar 4 at 4:46
  • \$\begingroup\$ @Davislor > I much prefer to have the templates detect when the recursion has gotten to objects of the same type as the argument to the reduction function, and eliminate the unwrap level parameter. Do you mean Automatic Type Deducing from Lambda? \$\endgroup\$
    – JimmyHu
    Mar 4 at 5:14
  • \$\begingroup\$ I’ve replied to at least one of your earlier posts in the series, I think the second or third one, with my own implementation. I seem to recall that it tested whether the value_type of the provided range was invocable with the provided transformation function. A similar approach would work on the reduction function, \$\endgroup\$
    – Davislor
    Mar 4 at 5:46

0

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