如何将std::vector的内容打印到屏幕上?


实现以下操作符<<的解决方案也很好:

template<container C, class T, String delim = ", ", String open = "[", String close = "]">
std::ostream & operator<<(std::ostream & o, const C<T> & x)
{
  // ... What can I write here?
}

以下是目前为止我所做的,没有单独的函数:

#include <iostream>
#include <fstream>
#include <string>
#include <cmath>
#include <vector>
#include <sstream>
#include <cstdio>
using namespace std;

int main()
{
    ifstream file("maze.txt");
    if (file) {
        vector<char> vec(istreambuf_iterator<char>(file), (istreambuf_iterator<char>()));
        vector<char> path;
        int x = 17;
        char entrance = vec.at(16);
        char firstsquare = vec.at(x);
        if (entrance == 'S') { 
            path.push_back(entrance); 
        }
        for (x = 17; isalpha(firstsquare); x++) {
            path.push_back(firstsquare);
        }
        for (int i = 0; i < path.size(); i++) {
            cout << path[i] << " ";
        }
        cout << endl;
        return 0;
    }
}

当前回答

只需将容器复制到控制台。

std::vector<int> v{1,2,3,4};
std::copy(v.begin(),v.end(),std::ostream_iterator<int>(std::cout, " " ));

应输出:

1 2 3 4

其他回答

从第一个BoostCon(现在叫CppCon)出来,我和另外两个人致力于一个库来实现这一点。主要的问题是需要扩展命名空间std。这对boost库来说是不可能的。

不幸的是,到代码的链接不再工作,但您可能会在讨论中发现一些有趣的花絮(至少那些没有讨论如何命名它!)

http://boost.2283326.n4.nabble.com/explore-Library-Proposal-Container-Streaming-td2619544.html

问题可能在前面的循环中:

(x = 17; isalpha(firstsquare); x++)

这个循环将根本不运行(如果firstsquare是非字母),或者将永远运行(如果它是字母)。原因是firstsquare不会随着x的增加而改变。

这些代码在现在的一些场合被证明是方便的,我觉得进入定制的费用是相当低的使用率。因此,我决定在MIT许可下发布它,并提供一个GitHub存储库,在那里可以下载头文件和一个小示例文件。

http://djmuw.github.io/prettycc

0. 前言和措辞

这个答案中的“装饰”是一组前缀字符串、分隔符字符串和后缀字符串。 其中,前缀字符串插入到流之前,后缀字符串插入到容器的值之后(参见2。目标容器)。 分隔符字符串被插入到各自容器的值之间。

注意:实际上,这个答案并没有将问题解决到100%,因为装饰并不是严格编译的时间常数,因为需要运行时检查来检查自定义装饰是否已应用到当前流。 不过,我认为它有一些不错的功能。

注2:可能有小错误,因为它还没有经过很好的测试。

1. 大意/使用

使用时不需要额外的代码

这是很容易做到的

#include <vector>
#include "pretty.h"

int main()
{
  std::cout << std::vector<int>{1,2,3,4,5}; // prints 1, 2, 3, 4, 5
  return 0;
}

易于定制…

... 对于特定的流对象

#include <vector>
#include "pretty.h"

int main()
{
  // set decoration for std::vector<int> for cout object
  std::cout << pretty::decoration<std::vector<int>>("(", ",", ")");
  std::cout << std::vector<int>{1,2,3,4,5}; // prints (1,2,3,4,5)
  return 0;
}

或者就所有流而言:

#include <vector>
#include "pretty.h"

// set decoration for std::vector<int> for all ostream objects
PRETTY_DEFAULT_DECORATION(std::vector<int>, "{", ", ", "}")

int main()
{
  std::cout << std::vector<int>{1,2,3,4,5}; // prints {1, 2, 3, 4, 5}
  std::cout << pretty::decoration<std::vector<int>>("(", ",", ")");
  std::cout << std::vector<int>{1,2,3,4,5}; // prints (1,2,3,4,5)
  return 0;
}

粗略的描述

该代码包括一个类模板,为任何类型提供默认装饰 可以专门改变(a)某些类型的默认装饰,它是 使用ios_base提供的私有存储,使用xalloc/pword来保存指向pretty::decor对象的指针,特别是在某个流上装饰某个类型。

如果没有pretty::decor<T此流的>对象已显式设置pretty:: defaults <T, charT, chartraitT>::decoration()被调用以获取给定类型的默认装饰。 类pretty:: defaults专门用于定制默认装饰。

2. 目标对象/容器

这段代码的“pretty decoration”的目标对象obj是具有这两种属性的对象

重载std::begin和std::end定义(包括c风格数组), 通过ADL提供begin(obj)和end(obj), 类型为std::tuple 或std::pair类型。

该代码包含一个trait,用于标识具有范围特征(begin/end)的类。 (但是没有检查begin(obj) == end(obj)是否为有效表达式。)

代码在全局命名空间中提供操作符<<s,仅应用于没有更专用版本的操作符<<可用的类。 因此,例如std::string虽然具有有效的开始/结束对,但在这段代码中不会使用操作符打印。

3.利用和定制

装饰可以分别施加给每种类型(除了不同的元组)和流(不是流类型!) (例如,std::vector<int>可以对不同的流对象有不同的装饰。)

A)默认装饰

默认前缀是""(什么都没有),默认后缀也是,而默认分隔符是","(逗号+空格)。

B)通过专门化漂亮的::defaults类模板定制一个类型的默认装饰

default结构体有一个静态成员函数decoration(),返回一个装潢对象,其中包含给定类型的默认值。

使用数组的示例:

自定义默认数组打印:

namespace pretty
{
  template<class T, std::size_t N>
  struct defaulted<T[N]>
  {
    static decor<T[N]> decoration()
    {
      return{ { "(" }, { ":" }, { ")" } };
    }
  };
}

打印一个数组:

float e[5] = { 3.4f, 4.3f, 5.2f, 1.1f, 22.2f };
std::cout << e << '\n'; // prints (3.4:4.3:5.2:1.1:22.2)

对字符流使用PRETTY_DEFAULT_DECORATION(TYPE, PREFIX, DELIM, POSTFIX,…)宏

宏展开为

namespace pretty { 
  template< __VA_ARGS__ >
  struct defaulted< TYPE > {
    static decor< TYPE > decoration() {
      return { PREFIX, DELIM, POSTFIX };
    } 
  }; 
} 

使上面的部分专门化可以重写为

PRETTY_DEFAULT_DECORATION(T[N], "", ";", "", class T, std::size_t N)

或者插入一个完整的专门化

PRETTY_DEFAULT_DECORATION(std::vector<int>, "(", ", ", ")")

wchar_t流的另一个宏包括:PRETTY_DEFAULT_WDECORATION。

C)对溪流进行装饰

函数pretty::decoration用于对某个流施加装饰。 两者都有超载 -一个字符串参数作为分隔符(采用默认类的前缀和后缀) -或三个字符串参数组合成完整的装饰

完整的装饰为给定类型和流

float e[3] = { 3.4f, 4.3f, 5.2f };
std::stringstream u;
// add { ; } decoration to u
u << pretty::decoration<float[3]>("{", "; ", "}");

// use { ; } decoration
u << e << '\n'; // prints {3.4; 4.3; 5.2}

// uses decoration returned by defaulted<float[3]>::decoration()
std::cout << e; // prints 3.4, 4.3, 5.2

自定义给定流的分隔符

PRETTY_DEFAULT_DECORATION(float[3], "{{{", ",", "}}}")

std::stringstream v;
v << e; // prints {{{3.4,4.3,5.2}}}

v << pretty::decoration<float[3]>(":");
v << e; // prints {{{3.4:4.3:5.2}}}

v << pretty::decoration<float[3]>("((", "=", "))");
v << e; // prints ((3.4=4.3=5.2))

4. 特殊处理std::tuple

这段代码没有允许对每一种可能的元组类型进行特化,而是将std::tuple<void*>可用的任何修饰应用到所有类型的std::tuple<…>s。

5. 从流中移除自定义装饰

要返回给定类型的默认装饰,请在流上使用pretty::clear函数模板。

s << pretty::clear<std::vector<int>>();

5. 进一步的例子

用换行分隔符打印“类似矩阵”

std::vector<std::vector<int>> m{ {1,2,3}, {4,5,6}, {7,8,9} };
std::cout << pretty::decoration<std::vector<std::vector<int>>>("\n");
std::cout << m;

打印

1, 2, 3
4, 5, 6
7, 8, 9

在ideone/KKUebZ上看到

6. 代码

#ifndef pretty_print_0x57547_sa4884X_0_1_h_guard_
#define pretty_print_0x57547_sa4884X_0_1_h_guard_

#include <string>
#include <iostream>
#include <type_traits>
#include <iterator>
#include <utility>

#define PRETTY_DEFAULT_DECORATION(TYPE, PREFIX, DELIM, POSTFIX, ...) \
    namespace pretty { template< __VA_ARGS__ >\
    struct defaulted< TYPE > {\
    static decor< TYPE > decoration(){\
      return { PREFIX, DELIM, POSTFIX };\
    } /*decoration*/ }; /*defaulted*/} /*pretty*/

#define PRETTY_DEFAULT_WDECORATION(TYPE, PREFIX, DELIM, POSTFIX, ...) \
    namespace pretty { template< __VA_ARGS__ >\
    struct defaulted< TYPE, wchar_t, std::char_traits<wchar_t> > {\
    static decor< TYPE, wchar_t, std::char_traits<wchar_t> > decoration(){\
      return { PREFIX, DELIM, POSTFIX };\
    } /*decoration*/ }; /*defaulted*/} /*pretty*/

namespace pretty
{

  namespace detail
  {
    // drag in begin and end overloads
    using std::begin;
    using std::end;
    // helper template
    template <int I> using _ol = std::integral_constant<int, I>*;
    // SFINAE check whether T is a range with begin/end
    template<class T>
    class is_range
    {
      // helper function declarations using expression sfinae
      template <class U, _ol<0> = nullptr>
      static std::false_type b(...);
      template <class U, _ol<1> = nullptr>
      static auto b(U &v) -> decltype(begin(v), std::true_type());
      template <class U, _ol<0> = nullptr>
      static std::false_type e(...);
      template <class U, _ol<1> = nullptr>
      static auto e(U &v) -> decltype(end(v), std::true_type());
      // return types
      using b_return = decltype(b<T>(std::declval<T&>()));
      using e_return = decltype(e<T>(std::declval<T&>()));
    public:
      static const bool value = b_return::value && e_return::value;
    };
  }

  // holder class for data
  template<class T, class CharT = char, class TraitT = std::char_traits<CharT>>
  struct decor
  {
    static const int xindex;
    std::basic_string<CharT, TraitT> prefix, delimiter, postfix;
    decor(std::basic_string<CharT, TraitT> const & pre = "",
      std::basic_string<CharT, TraitT> const & delim = "",
      std::basic_string<CharT, TraitT> const & post = "")
      : prefix(pre), delimiter(delim), postfix(post) {}
  };

  template<class T, class charT, class traits>
  int const decor<T, charT, traits>::xindex = std::ios_base::xalloc();

  namespace detail
  {

    template<class T, class CharT, class TraitT>
    void manage_decor(std::ios_base::event evt, std::ios_base &s, int const idx)
    {
      using deco_type = decor<T, CharT, TraitT>;
      if (evt == std::ios_base::erase_event)
      { // erase deco
        void const * const p = s.pword(idx);
        if (p)
        {
          delete static_cast<deco_type const * const>(p);
          s.pword(idx) = nullptr;
        }
      }
      else if (evt == std::ios_base::copyfmt_event)
      { // copy deco
        void const * const p = s.pword(idx);
        if (p)
        {
          auto np = new deco_type{ *static_cast<deco_type const * const>(p) };
          s.pword(idx) = static_cast<void*>(np);
        }
      }
    }

    template<class T> struct clearer {};

    template<class T, class CharT, class TraitT>
    std::basic_ostream<CharT, TraitT>& operator<< (
      std::basic_ostream<CharT, TraitT> &s, clearer<T> const &)
    {
      using deco_type = decor<T, CharT, TraitT>;
      void const * const p = s.pword(deco_type::xindex);
      if (p)
      { // delete if set
        delete static_cast<deco_type const *>(p);
        s.pword(deco_type::xindex) = nullptr;
      }
      return s;
    }

    template <class CharT> 
    struct default_data { static const CharT * decor[3]; };
    template <> 
    const char * default_data<char>::decor[3] = { "", ", ", "" };
    template <> 
    const wchar_t * default_data<wchar_t>::decor[3] = { L"", L", ", L"" };

  }

  // Clear decoration for T
  template<class T>
  detail::clearer<T> clear() { return{}; }
  template<class T, class CharT, class TraitT>
  void clear(std::basic_ostream<CharT, TraitT> &s) { s << detail::clearer<T>{}; }

  // impose decoration on ostream
  template<class T, class CharT, class TraitT>
  std::basic_ostream<CharT, TraitT>& operator<<(
    std::basic_ostream<CharT, TraitT> &s, decor<T, CharT, TraitT> && h)
  {
    using deco_type = decor<T, CharT, TraitT>;
    void const * const p = s.pword(deco_type::xindex);
    // delete if already set
    if (p) delete static_cast<deco_type const *>(p);
    s.pword(deco_type::xindex) = static_cast<void *>(new deco_type{ std::move(h) });
    // check whether we alread have a callback registered
    if (s.iword(deco_type::xindex) == 0)
    { // if this is not the case register callback and set iword
      s.register_callback(detail::manage_decor<T, CharT, TraitT>, deco_type::xindex);
      s.iword(deco_type::xindex) = 1;
    }
    return s;
  }

  template<class T, class CharT = char, class TraitT = std::char_traits<CharT>>
  struct defaulted
  {
    static inline decor<T, CharT, TraitT> decoration()
    {
      return{ detail::default_data<CharT>::decor[0],
        detail::default_data<CharT>::decor[1],
        detail::default_data<CharT>::decor[2] };
    }
  };

  template<class T, class CharT = char, class TraitT = std::char_traits<CharT>>
  decor<T, CharT, TraitT> decoration(
    std::basic_string<CharT, TraitT> const & prefix,
    std::basic_string<CharT, TraitT> const & delimiter,
    std::basic_string<CharT, TraitT> const & postfix)
  {
    return{ prefix, delimiter, postfix };
  }

  template<class T, class CharT = char,
  class TraitT = std::char_traits < CharT >>
    decor<T, CharT, TraitT> decoration(
      std::basic_string<CharT, TraitT> const & delimiter)
  {
    using str_type = std::basic_string<CharT, TraitT>;
    return{ defaulted<T, CharT, TraitT>::decoration().prefix,
      delimiter, defaulted<T, CharT, TraitT>::decoration().postfix };
  }

  template<class T, class CharT = char,
  class TraitT = std::char_traits < CharT >>
    decor<T, CharT, TraitT> decoration(CharT const * const prefix,
      CharT const * const delimiter, CharT const * const postfix)
  {
    using str_type = std::basic_string<CharT, TraitT>;
    return{ str_type{ prefix }, str_type{ delimiter }, str_type{ postfix } };
  }

  template<class T, class CharT = char,
  class TraitT = std::char_traits < CharT >>
    decor<T, CharT, TraitT> decoration(CharT const * const delimiter)
  {
    using str_type = std::basic_string<CharT, TraitT>;
    return{ defaulted<T, CharT, TraitT>::decoration().prefix,
      str_type{ delimiter }, defaulted<T, CharT, TraitT>::decoration().postfix };
  }

  template<typename T, std::size_t N, std::size_t L>
  struct tuple
  {
    template<class CharT, class TraitT>
    static void print(std::basic_ostream<CharT, TraitT>& s, T const & value,
      std::basic_string<CharT, TraitT> const &delimiter)
    {
      s << std::get<N>(value) << delimiter;
      tuple<T, N + 1, L>::print(s, value, delimiter);
    }
  };

  template<typename T, std::size_t N>
  struct tuple<T, N, N>
  {
    template<class CharT, class TraitT>
    static void print(std::basic_ostream<CharT, TraitT>& s, T const & value,
      std::basic_string<CharT, TraitT> const &) {
      s << std::get<N>(value);
    }
  };

}

template<class CharT, class TraitT>
std::basic_ostream<CharT, TraitT> & operator<< (
  std::basic_ostream<CharT, TraitT> &s, std::tuple<> const & v)
{
  using deco_type = pretty::decor<std::tuple<void*>, CharT, TraitT>;
  using defaulted_type = pretty::defaulted<std::tuple<void*>, CharT, TraitT>;
  void const * const p = s.pword(deco_type::xindex);
  auto const d = static_cast<deco_type const * const>(p);
  s << (d ? d->prefix : defaulted_type::decoration().prefix);
  s << (d ? d->postfix : defaulted_type::decoration().postfix);
  return s;
}

template<class CharT, class TraitT, class ... T>
std::basic_ostream<CharT, TraitT> & operator<< (
  std::basic_ostream<CharT, TraitT> &s, std::tuple<T...> const & v)
{
  using deco_type = pretty::decor<std::tuple<void*>, CharT, TraitT>;
  using defaulted_type = pretty::defaulted<std::tuple<void*>, CharT, TraitT>;
  using pretty_tuple = pretty::tuple<std::tuple<T...>, 0U, sizeof...(T)-1U>;
  void const * const p = s.pword(deco_type::xindex);
  auto const d = static_cast<deco_type const * const>(p);
  s << (d ? d->prefix : defaulted_type::decoration().prefix);
  pretty_tuple::print(s, v, d ? d->delimiter : 
    defaulted_type::decoration().delimiter);
  s << (d ? d->postfix : defaulted_type::decoration().postfix);
  return s;
}

template<class T, class U, class CharT, class TraitT>
std::basic_ostream<CharT, TraitT> & operator<< (
  std::basic_ostream<CharT, TraitT> &s, std::pair<T, U> const & v)
{
  using deco_type = pretty::decor<std::pair<T, U>, CharT, TraitT>;
  using defaulted_type = pretty::defaulted<std::pair<T, U>, CharT, TraitT>;
  void const * const p = s.pword(deco_type::xindex);
  auto const d = static_cast<deco_type const * const>(p);
  s << (d ? d->prefix : defaulted_type::decoration().prefix);
  s << v.first;
  s << (d ? d->delimiter : defaulted_type::decoration().delimiter);
  s << v.second;
  s << (d ? d->postfix : defaulted_type::decoration().postfix);
  return s;
}


template<class T, class CharT = char,
class TraitT = std::char_traits < CharT >>
  typename std::enable_if < pretty::detail::is_range<T>::value,
  std::basic_ostream < CharT, TraitT >> ::type & operator<< (
    std::basic_ostream<CharT, TraitT> &s, T const & v)
{
  bool first(true);
  using deco_type = pretty::decor<T, CharT, TraitT>;
  using default_type = pretty::defaulted<T, CharT, TraitT>;
  void const * const p = s.pword(deco_type::xindex);
  auto d = static_cast<pretty::decor<T, CharT, TraitT> const * const>(p);
  s << (d ? d->prefix : default_type::decoration().prefix);
  for (auto const & e : v)
  { // v is range thus range based for works
    if (!first) s << (d ? d->delimiter : default_type::decoration().delimiter);
    s << e;
    first = false;
  }
  s << (d ? d->postfix : default_type::decoration().postfix);
  return s;
}

#endif // pretty_print_0x57547_sa4884X_0_1_h_guard_

模板收集:

应用std::cout <<和std::to_string

std::vector、std::array和std::tuple

由于在cpp中打印一个向量被证明是惊人的工作量(至少与这个任务的基本程度相比),并且作为再次跨越相同问题的一个步骤,当使用其他容器时,这里有一个更通用的解决方案…

模板收集内容

这个模板集合处理3种容器类型: Std::vector, Std::array和Std::tuple。 它为这些对象定义了std::to_string(),并可以通过std::cout << container;直接将它们打印出来。

此外,它还为std::string << container定义了<<运算符。 这样就可以以紧凑的方式构造包含这些容器类型的字符串。

From

std::string s1 = "s1: " + std::to_string(arr) + "; " + std::to_string(vec) + "; " + std::to_string(tup);

我们会讲到

std::string s2 = STR() << "s2: " << arr << "; " << vec << "; " << tup;

Code

您可以交互地测试这段代码:这里。

#include <iostream>
#include <string>
#include <tuple>
#include <vector>
#include <array>

namespace std
{   
    // declations: needed for std::to_string(std::vector<std::tuple<int, float>>)
    std::string to_string(std::string str);
    std::string to_string(const char *str);
    template<typename T, size_t N>
    std::string to_string(std::array<T, N> const& arr);
    template<typename T>
    std::string to_string(std::vector<T> const& vec);
    template<typename... Args>
    std::string to_string(const std::tuple<Args...>& tup);
    
    std::string to_string(std::string str)
    {
        return std::string(str);
    }
    std::string to_string(const char *str)
    {
        return std::string(str);
    }

    template<typename T, size_t N>
    std::string to_string(std::array<T, N> const& arr)
    {
        std::string s="{";
        for (std::size_t t = 0; t != N; ++t)
            s += std::to_string(arr[t]) + (t+1 < N ? ", ":"");
        return s + "}";
    }

    template<typename T>
    std::string to_string(std::vector<T> const& vec)
    {
        std::string s="[";
        for (std::size_t t = 0; t != vec.size(); ++t)
            s += std::to_string(vec[t]) + (t+1 < vec.size() ? ", ":"");
        return s + "]";
    }
    
    // to_string(tuple)
    // https://en.cppreference.com/w/cpp/utility/tuple/operator%3D
    template<class Tuple, std::size_t N>
    struct TupleString
    {
        static std::string str(const Tuple& tup)
        {
            std::string out;
            out += TupleString<Tuple, N-1>::str(tup);
            out += ", ";
            out += std::to_string(std::get<N-1>(tup));
            return out;
        }
    };
    template<class Tuple>
    struct TupleString<Tuple, 1>
    {
        static std::string str(const Tuple& tup)
        {
            std::string out;
            out += std::to_string(std::get<0>(tup));
            return out;
        }
    };
    template<typename... Args>
    std::string to_string(const std::tuple<Args...>& tup)
    {
        std::string out = "(";
        out += TupleString<decltype(tup), sizeof...(Args)>::str(tup);
        out += ")";
        return out;
    }
} // namespace std


/**
 * cout: cout << continer
 */
template <typename T, std::size_t N> // cout << array
std::ostream& operator <<(std::ostream &out, std::array<T, N> &con)
{
    out <<  std::to_string(con);
    return out;
}
template <typename T, typename A> // cout << vector
std::ostream& operator <<(std::ostream &out, std::vector<T, A> &con)
{
    out <<  std::to_string(con);
    return out;
}
template<typename... Args> // cout << tuple
std::ostream& operator <<(std::ostream &out, std::tuple<Args...> &con)
{
    out <<  std::to_string(con);
    return out;
}

/**
 * Concatenate: string << continer
 */
template <class C>
std::string operator <<(std::string str, C &con)
{
    std::string out = str;
    out += std::to_string(con);
    return out;
}
#define STR() std::string("")

int main()
{
    std::array<int, 3> arr {1, 2, 3};
    std::string sArr = std::to_string(arr);
    std::cout << "std::array" << std::endl;
    std::cout << "\ttest to_string: " << sArr << std::endl;
    std::cout << "\ttest cout <<: " << arr << std::endl;
    std::cout << "\ttest string <<: " << (std::string() << arr) << std::endl;
    
    std::vector<std::string> vec {"a", "b"};
    std::string sVec = std::to_string(vec);
    std::cout << "std::vector" << std::endl;
    std::cout << "\ttest to_string: " << sVec << std::endl;
    std::cout << "\ttest cout <<: " << vec << std::endl;
    std::cout << "\ttest string <<: " << (std::string() << vec) << std::endl;
    
    std::tuple<int, std::string> tup = std::make_tuple(5, "five");
    std::string sTup = std::to_string(tup);
    std::cout << "std::tuple" << std::endl;
    std::cout << "\ttest to_string: " << sTup << std::endl;
    std::cout << "\ttest cout <<: " << tup << std::endl;
    std::cout << "\ttest string <<: " << (std::string() << tup) << std::endl;
    
    std::vector<std::tuple<int, float>> vt {std::make_tuple(1, .1), std::make_tuple(2, .2)};
    std::string sVt = std::to_string(vt);
    std::cout << "std::vector<std::tuple>" << std::endl;
    std::cout << "\ttest to_string: " << sVt << std::endl;
    std::cout << "\ttest cout <<: " << vt << std::endl;
    std::cout << "\ttest string <<: " << (std::string() << vt) << std::endl;
    
    std::cout << std::endl;
    
    std::string s1 = "s1: " + std::to_string(arr) + "; " + std::to_string(vec) + "; " + std::to_string(tup);
    std::cout << s1 << std::endl;
    
    std::string s2 = STR() << "s2: " << arr << "; " << vec << "; " << tup;
    std::cout << s2 << std::endl;

    return 0;
}

输出

std::array
    test to_string: {1, 2, 3}
    test cout <<: {1, 2, 3}
    test string <<: {1, 2, 3}
std::vector
    test to_string: [a, b]
    test cout <<: [a, b]
    test string <<: [a, b]
std::tuple
    test to_string: (5, five)
    test cout <<: (5, five)
    test string <<: (5, five)
std::vector<std::tuple>
    test to_string: [(1, 0.100000), (2, 0.200000)]
    test cout <<: [(1, 0.100000), (2, 0.200000)]
    test string <<: [(1, 0.100000), (2, 0.200000)]

s1: {1, 2, 3}; [a, b]; (5, five)
s2: {1, 2, 3}; [a, b]; (5, five)

对于想要没有循环的一行程序的人:

我不敢相信没有人知道这一点,但也许是因为更像c的方法。不管怎样,在没有循环的情况下,假设std::vector<char>是空终止的,在一行程序中是完全安全的:

std::vector<char> test { 'H', 'e', 'l', 'l', 'o', ',', ' ', 'w', 'o', 'r', 'l', 'd', '!', '\0' };
std::cout << test.data() << std::endl;

但为了安全起见,我会把它包装在ostream操作符中,就像@Zorawar建议的那样:

template <typename T>std::ostream& operator<< (std::ostream& out, std::vector<T>& v)
{
    v.push_back('\0'); // safety-check!
    out << v.data();
    return out;
}

std::cout << test << std::endl; // will print 'Hello, world!'

我们可以通过使用printf来实现类似的行为:

fprintf(stdout, "%s\n", &test[0]); // will also print 'Hello, world!'

注意:

重载的ostream操作符需要接受非const的vector。这可能会使程序不安全或引入不可用的代码。此外,由于添加了空字符,可能会发生std::vector的重新分配。因此,使用带有迭代器的for循环可能会更快。