相关疑难解决方法(0)

#include <vector>
#include <iostream>
#include <range/v3/all.hpp>

int main()
{
    auto coll = std::vector{ 1, 2, 3 };

    ranges::copy(
        coll,
        ranges::ostream_iterator<int>{  std::cout, ", " }
    ); // ok

    ranges::copy(
        coll, 
        std::ostream_iterator<int>{ std::cout, ", " }
    ); // error 
}

问题显示在上面的代码中.我使用range-v3-0.3.7.

对我来说,通用算法copy不应该关心目标迭代器类型,只要它满足输出迭代器的要求即可.

如果是这样,为什么范围的算法不与std的迭代器兼容？

为什么新std::sentinel_for概念要求哨兵类型是default_initializable(via semiregular)？这是否排除了一大类有用的哨兵类型，其中默认构造没有任何意义？

例子：

//Iterate over a string until given character or '\0' is found
class char_sentinel
{
public:
    char_sentinel(char end) :
        end_character(end)
    { }

   friend bool operator==(const char* lhs, char_sentinel rhs)
   {
       return (*lhs == '\0') || (*lhs == rhs.end_character);
   }

   friend bool operator!=(const char* lhs, char_sentinel rhs) { ... }
   friend bool operator==(char_sentinel lhs, const char* rhs) { ... }
   friend bool operator!=(char_sentinel lhs, const char* rhs) { ... }

private:
    char end_character; 
}; …