C++ 使用boosthof实现STL打印

任意类型的漂亮打印容器

以下几行代码提供与中相同的输出， 但输出流仅限于

std:：cout

如何使用

boost:：hof

重写这些代码，以提供

print（std:：ostream&，…）

类似的接口

#包括
#包括
BOOST\u HOF\u STATIC\u LAMBDA\u函数（简单打印）=//BOOST:：HOF:：proj(
boost：：hof：：fix（boost：：hof：：的第一个(
[]（auto，const auto&x）->decltype（std:：cout只需添加一个参数来传递ostream就足够了：

BOOST_HOF_STATIC_LAMBDA_FUNCTION(simple_print_ex) = boost::hof::fix(
    boost::hof::first_of(
        [](auto, auto& os, const auto &x) -> decltype(os << x, void()) { os << x; },
        [](auto self, auto& os, const auto &range) -> decltype(self(os, *std::begin(range)), void()) {
            bool sep = false;
            os << '{';
            for (const auto &x : range) {
                sep = !sep || os << ',';
                self(os, x);
            }
            os << '}';
        },
        [](auto self, auto& os, const auto &tuple) {
            using namespace boost::hof;
            os << '(';
            bool sep = false;
            unpack(proj([&](const auto &i) {
                sep = !sep || os << ',';
                self(os, i);
            }))(tuple);
            os << ')';
        }));

template <typename Ostream, typename... Args> void print_ex(Ostream& os, Args &&... args) { simple_print_ex(os, std::make_tuple(std::forward<Args>(args)...)); }

表册

std::ofstream ofs("test.txt");
print_ex(ofs, t3, "xxxx", 55, m, std::vector<std::string>{ "x" }, XX{ 66 });
ofs << "\n";

#include <boost/hof.hpp>
#include <iostream>

BOOST_HOF_STATIC_LAMBDA_FUNCTION(simple_print_ex) = boost::hof::fix(
    boost::hof::first_of(
        [](auto, auto& os, const auto &x) -> decltype(os << x, void()) { os << x; },
        [](auto self, auto& os, const auto &range) -> decltype(self(os, *std::begin(range)), void()) {
            bool sep = false;
            os << '{';
            for (const auto &x : range) {
                sep = !sep || os << ',';
                self(os, x);
            }
            os << '}';
        },
        [](auto self, auto& os, const auto &tuple) {
            using namespace boost::hof;
            os << '(';
            bool sep = false;
            unpack(proj([&](const auto &i) {
                sep = !sep || os << ',';
                self(os, i);
            }))(tuple);
            os << ')';
        }));

template <typename Ostream, typename... Args> void print_ex(Ostream& os, Args &&... args) { simple_print_ex(os, std::make_tuple(std::forward<Args>(args)...)); }
template <typename... Args> void print(Args &&... args) { print_ex(std::cout, std::forward<Args>(args)...); }

//---- user code ---
struct XX {
    int n = 0;

    friend std::ostream &operator<<(std::ostream &os, const XX &o) { return os << o.n << "XX"; }
};

#include <map>
#include <vector>
#include <fstream>
int main() {
    using namespace std::string_literals;

    std::vector v = { 1, 2, 3, 4 };
    std::map m { std::pair { "a"s, 30 }, { "bb", 31 }, { "ccc", 32 } };

    auto t = std::make_tuple(6, 7, 8, 9);
    auto t2 = std::make_tuple(11, std::ref(v), t);
    auto t3 = std::make_tuple(t2, std::vector{ 1234, 23, 2, 3, 3 }, "abc",
                              std::vector{ std::vector{ 11, 12, 13 }, std::vector{ 15, 16, 17 }, std::vector{ 19 } });
    std::ofstream ofs("test.txt");
    print_ex(ofs, t3, "xxxx", 55, m, std::vector<std::string>{ "x" }, XX{ 66 });
    ofs << "\n";

    print(t3, "xxxx", 55, m, std::vector<std::string>{ "x" }, XX{ 66 });
}

#包括
#包括
BOOST_HOF_STATIC_LAMBDA_函数（简单打印）=BOOST:：HOF:：fix(
boost：：hof：：第一个(
[]（auto，auto&os，const auto&x）->decltype（os谢谢你的回答。通过你的代码，我找到了阻止我添加Ostream参数的原因，这是第一个
boost:：hof:：proj
旨在实现
模板无效打印（Args&…Args）{simple_打印（std:：forward（Args）；}
。
#include <boost/hof.hpp>
#include <iostream>

BOOST_HOF_STATIC_LAMBDA_FUNCTION(simple_print_ex) = boost::hof::fix(
    boost::hof::first_of(
        [](auto, auto& os, const auto &x) -> decltype(os << x, void()) { os << x; },
        [](auto self, auto& os, const auto &range) -> decltype(self(os, *std::begin(range)), void()) {
            bool sep = false;
            os << '{';
            for (const auto &x : range) {
                sep = !sep || os << ',';
                self(os, x);
            }
            os << '}';
        },
        [](auto self, auto& os, const auto &tuple) {
            using namespace boost::hof;
            os << '(';
            bool sep = false;
            unpack(proj([&](const auto &i) {
                sep = !sep || os << ',';
                self(os, i);
            }))(tuple);
            os << ')';
        }));

template <typename Ostream, typename... Args> void print_ex(Ostream& os, Args &&... args) { simple_print_ex(os, std::make_tuple(std::forward<Args>(args)...)); }
template <typename... Args> void print(Args &&... args) { print_ex(std::cout, std::forward<Args>(args)...); }

//---- user code ---
struct XX {
    int n = 0;

    friend std::ostream &operator<<(std::ostream &os, const XX &o) { return os << o.n << "XX"; }
};

#include <map>
#include <vector>
#include <fstream>
int main() {
    using namespace std::string_literals;

    std::vector v = { 1, 2, 3, 4 };
    std::map m { std::pair { "a"s, 30 }, { "bb", 31 }, { "ccc", 32 } };

    auto t = std::make_tuple(6, 7, 8, 9);
    auto t2 = std::make_tuple(11, std::ref(v), t);
    auto t3 = std::make_tuple(t2, std::vector{ 1234, 23, 2, 3, 3 }, "abc",
                              std::vector{ std::vector{ 11, 12, 13 }, std::vector{ 15, 16, 17 }, std::vector{ 19 } });
    std::ofstream ofs("test.txt");
    print_ex(ofs, t3, "xxxx", 55, m, std::vector<std::string>{ "x" }, XX{ 66 });
    ofs << "\n";

    print(t3, "xxxx", 55, m, std::vector<std::string>{ "x" }, XX{ 66 });
}