A recursive_all_of Template Function with Unwrap Level Implementation in C++

Question

This is a follow-up question for A recursive_find_if_all Template Function Implementation in C++ and A recursive_all_of Template Function Implementation in C++. To support std::string, std::wstring, std::u8string and std::pmr::string (making recursive_all_of template function more generic), I am trying to implement recursive_all_of template function with unwrap level in this post.

The experimental implementation

recursive_all_of Template Function

/*  recursive_all_of template function implementation with unwrap level
*/
template<std::size_t unwrap_level, class T, class Proj = std::identity, class UnaryPredicate>
requires(unwrap_level <= recursive_depth<T>())
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));
    }
}

Full Testing Code

The full testing code:

//  A recursive_all_of template function implementation with unwrap level

#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 <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};
}

/*  recursive_foreach_all template function performs specific function on input container exhaustively
    https://codereview.stackexchange.com/a/286525/231235
*/
namespace impl {

    template<class F, class Proj = std::identity>
    struct recursive_for_each_state {
        F f;
        Proj proj;
    };

    //  recursive_foreach_all template function implementation
    template<class T, class State>
    requires (recursive_depth<T>() == 0)
    constexpr void recursive_foreach_all(T& value, State& state) {
        std::invoke(state.f, std::invoke(state.proj, value));
    }

    template<class T, class State>
    requires (recursive_depth<T>() != 0)
    constexpr void recursive_foreach_all(T& inputRange, State& state) {
        for (auto& item: inputRange)
            impl::recursive_foreach_all(item, state);
    }

    //  recursive_reverse_foreach_all template function implementation
    template<class T, class State>
    requires (recursive_depth<T>() == 0)
    constexpr void recursive_reverse_foreach_all(T& value, State& state) {
        std::invoke(state.f, std::invoke(state.proj, value));
    }

    template<class T, class State>
    requires (recursive_depth<T>() != 0)
    constexpr void recursive_reverse_foreach_all(T& inputRange, State& state) {
        for (auto& item: inputRange | std::views::reverse)
            impl::recursive_reverse_foreach_all(item, state);
    }
}

template<class T, class Proj = std::identity, class F>
constexpr auto recursive_foreach_all(T& inputRange, F f, Proj proj = {})
{
    impl::recursive_for_each_state state(std::move(f), std::move(proj));
    impl::recursive_foreach_all(inputRange, state);
    return std::make_pair(inputRange.end(), std::move(state.f));
}

template<class T, class Proj = std::identity, class F>
constexpr auto recursive_reverse_foreach_all(T& inputRange, F f, Proj proj = {})
{
    impl::recursive_for_each_state state(std::move(f), std::move(proj));
    impl::recursive_reverse_foreach_all(inputRange, state);
    return std::make_pair(inputRange.end(), std::move(state.f));
}

template<class T, class I, class F>
constexpr auto recursive_fold_left_all(const T& inputRange, I init, F f)
{
    recursive_foreach_all(inputRange, [&](auto& value) {
        init = std::invoke(f, init, value);
    });

    return init;
}

template<class T, class I, class F>
constexpr auto recursive_fold_right_all(const T& inputRange, I init, F f)
{
    recursive_reverse_foreach_all(inputRange, [&](auto& value) {
        init = std::invoke(f, value, init);
    });

    return init;
}

//  recursive_count_if template function implementation
template<class T, std::invocable<T> Pred>
requires (recursive_depth<T>() == 0)
constexpr std::size_t recursive_count_if_all(const T& input, const Pred& predicate)
{
    return predicate(input) ? std::size_t{1} : std::size_t{0};
}

template<std::ranges::input_range Range, class Pred>
requires (recursive_depth<Range>() != 0)
constexpr auto recursive_count_if_all(const Range& input, const Pred& predicate)
{
    return std::transform_reduce(std::ranges::cbegin(input), std::ranges::cend(input), std::size_t{}, std::plus<std::size_t>(), [predicate](auto&& element) {
        return recursive_count_if_all(element, predicate);
        });
}

template<std::size_t unwrap_level, class T, class Pred>
requires(unwrap_level <= recursive_depth<T>())
constexpr auto recursive_count_if(const T& input, const Pred& predicate)
{
    if constexpr (unwrap_level > 0)
    {
        return std::transform_reduce(std::ranges::cbegin(input), std::ranges::cend(input), std::size_t{}, std::plus<std::size_t>(), [predicate](auto&& element) {
            return recursive_count_if<unwrap_level - 1>(element, predicate);
            });
    }
    else
    {
        return predicate(input) ? 1 : 0;
    }
    
}

/*  recursive_all_of template function implementation with unwrap level
*/
template<std::size_t unwrap_level, class T, class Proj = std::identity, class UnaryPredicate>
requires(unwrap_level <= recursive_depth<T>())
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));
    }
}

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(input.cbegin(), input.cend(), 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;
}

void recursive_all_of_tests()
{
    auto test_vectors_1 = n_dim_container_generator<4, int, std::vector>(1, 3);
    test_vectors_1[0][0][0][0] = 2;
    assert(recursive_all_of<4>(test_vectors_1, [](auto&& i) { return i % 2 == 0; }) == false);

    auto test_vectors_2 = n_dim_container_generator<4, int, std::vector>(2, 3);
    test_vectors_2[0][0][0][0] = 4;
    assert(recursive_all_of<4>(test_vectors_2, [](auto&& i) { return i % 2 == 0; }));
    
    //  Tests with std::string
    auto test_vector_string = n_dim_container_generator<4, std::string, std::vector>("1", 3);
    assert(recursive_all_of<4>(test_vector_string, [](auto&& i) { return i == "1"; }));
    assert(recursive_all_of<4>(test_vector_string, [](auto&& i) { return i == "2"; }) == false);

    //  Tests with std::string, projection
    assert(recursive_all_of<4>(
        test_vector_string,
        [](auto&& i) { return i == "1"; },
        [](auto&& element) {return std::to_string(stoi(element) + 1); }) == false);
    assert(recursive_all_of<4>(
        test_vector_string,
        [](auto&& i) { return i == "2"; },
        [](auto&& element) {return std::to_string(stoi(element) + 1); }));
    
    //  Tests with std::array of std::string
    std::array<std::string, 3> word_array1 = {"foo", "foo", "foo"};
    assert(recursive_all_of<1>(word_array1, [](auto&& i) { return i == "foo"; }));
    assert(recursive_all_of<1>(word_array1, [](auto&& i) { return i == "bar"; }) == false);

    //  Tests with std::deque of std::string
    std::deque<std::string> word_deque1 = {"foo", "foo", "foo", "foo"};
    assert(recursive_all_of<1>(word_deque1, [](auto&& i) { return i == "foo"; }));
    assert(recursive_all_of<1>(word_deque1, [](auto&& i) { return i == "bar"; }) == false);

    std::vector<std::wstring> wstring_vector1{};
    for(int i = 0; i < 4; ++i)
    {
        wstring_vector1.push_back(std::to_wstring(1));
    }
    assert(recursive_all_of<1>(wstring_vector1, [](auto&& i) { return i == std::to_wstring(1); }));
    assert(recursive_all_of<1>(wstring_vector1, [](auto&& i) { return i == std::to_wstring(2); }) == false);

    std::vector<std::u8string> u8string_vector1{};
    for(int i = 0; i < 4; ++i)
    {
        u8string_vector1.push_back(u8"\u20AC2.00");
    }
    assert(recursive_all_of<1>(u8string_vector1, [](auto&& i) { return i == u8"\u20AC2.00"; }));
    assert(recursive_all_of<1>(u8string_vector1, [](auto&& i) { return i == u8"\u20AC1.00"; }) == false);

    std::pmr::string pmr_string1 = "123";
    std::vector<std::pmr::string> pmr_string_vector1 = {pmr_string1, pmr_string1, pmr_string1};
    assert(recursive_all_of<1>(pmr_string_vector1, [](auto&& i) { return i == "123"; }));
    assert(recursive_all_of<1>(pmr_string_vector1, [](auto&& i) { return i == "456"; }) == false);
    std::cout << "All tests passed!\n";


    return;
}

int main()
{
    auto start = std::chrono::system_clock::now();
    recursive_all_of_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 0;
}

The output of the test code above:

All tests passed!
Computation finished at Mon Jan 29 13:52:59 2024
elapsed time: 4.7914e-05

Godbolt link is here.

All suggestions are welcome.

The summary information:

Which question it is a follow-up to?

A recursive_find_if_all Template Function Implementation in C++ and

A recursive_all_of Template Function Implementation in C++
What changes has been made in the code since last question?

I am trying to implement recursive_all_of template function with unwrap level in this post.
Why a new review is being asked for?

Please review the revised recursive_all_of template function and its tests. All suggestions are welcome.

G. Sliepen · Accepted Answer · 2024-01-30 15:19:11Z

0

This looks very good. The only issue I can see is that you did not constrain the types Proj and UnaryPredicate. That means that if you provide an incorrect projection and/or predicate, you will get an error message at the deepest level of recursion, which will likely result in a hard to read error message. It would be great if you could constrain the allowed types of these template parameters somehow.

answered Jan 30 at 15:19

G. Sliepen

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