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

在c++ 11中,你现在可以使用一个基于范围的for循环:

for (auto const& c : path)
    std::cout << c << ' ';

其他回答

我的解决方案是simple.h,它是scc包的一部分。所有std容器,map, set, c-arrays都是可打印的。

重载操作符< <:

template<typename OutStream, typename T>
OutStream& operator<< (OutStream& out, const vector<T>& v)
{
    for (auto const& tmp : v)
        out << tmp << " ";
    out << endl;
    return out;
}

用法:

vector <int> test {1,2,3};
wcout << test; // or any output stream

我将在这里添加另一个答案,因为我已经提出了与之前的方法不同的方法,那就是使用locale facet。

基本原理在这里

基本上你要做的是:

Create a class that derives from std::locale::facet. The slight downside is that you will need a compilation unit somewhere to hold its id. Let's call it MyPrettyVectorPrinter. You'd probably give it a better name, and also create ones for pair and map. In your stream function, you check std::has_facet< MyPrettyVectorPrinter > If that returns true, extract it with std::use_facet< MyPrettyVectorPrinter >( os.getloc() ) Your facet objects will have values for the delimiters and you can read them. If the facet isn't found, your print function (operator<<) provides default ones. Note you can do the same thing for reading a vector.

我喜欢这种方法,因为你可以使用默认打印,同时仍然能够使用自定义覆盖。

缺点是如果在多个项目中使用facet,则需要一个面向facet的库(因此不能仅仅是头文件),而且需要注意创建一个新的locale对象的开销。

我把这个作为一个新的解决方案来写,而不是修改我的另一个解决方案,因为我相信两种方法都是正确的,你可以选择。

template <typename T>
std::ostream& operator<<( std::ostream& ostrm, const std::vector<T>& vec ){
    ostrm << "[";
    for( int j = 0, n = vec.size(); j < n; ++j ){
        ostrm << " " << vec[ j ] << " ,"[ j < n - 1 ];
    }
    return ostrm << "]";
}

[1, 2, 3, 4]

如果boost是一个选项,那么你可以使用boost::algorithm::join。例如,打印std::string的向量:

#include <boost/algorithm/string/join.hpp>

std::vector<std::string> vs { "some", "string", "vector" };
std::cout << boost::algorithm::join(vs, " | ") << '\n';

对于其他类型的向量,首先需要转换为字符串

#include <algorithm>
#include <iostream>
#include <numeric>
#include <vector>

#include <boost/algorithm/string/join.hpp>
#include <boost/range/adaptor/transformed.hpp>

int main()
{
    using boost::adaptors::transformed;
    using boost::algorithm::join;

    // Generate the vector
    std::vector<int> vi(10);
    std::iota(vi.begin(), vi.end(), -3);

    // Print out the vector
    std::cout << join(vi |
                 transformed(static_cast<std::string(*)(int)>(std::to_string)),
                 ", ")
              << '\n';
}

Godbolt演示