c++ - std::insert_iterator 和迭代器失效

Question

我尝试编写一个通用的、就地的、intersperse 函数。该函数应将给定元素散布到一系列元素中。

#include <vector>
#include <list>
#include <algorithm>
#include <iostream>

template<typename ForwardIterator, typename InserterFunc>
void intersperse(ForwardIterator begin, ForwardIterator end, InserterFunc ins, 
                 // we cannot use rvalue references here, 
                 // maybe taking by value and letting users feed in std::ref would be smarter
                 const ForwardIterator::value_type& elem) {
  if(begin == end) return;
  while(++begin != end) {
    // bugfix would be something like:
    // begin = (ins(begin) = elem); // insert_iterator is convertible to a normal iterator
    // or
    // begin = (ins(begin) = elem).iterator(); // get the iterator to the last inserted element

    // begin now points to the inserted element and we need to
    // increment the iterator once again, which is safe
    // ++begin;
    ins(begin) = elem;
  }
}

int main()
{
  typedef std::list<int> container;
  // as expected tumbles, falls over and goes up in flames with:
  // typedef std::vector<int> container;
  typedef container::iterator iterator;
  container v{1,2,3,4};

  intersperse(v.begin(), v.end(), 
              [&v](iterator it) { return std::inserter(v, it); },
              23);
  for(auto x : v)
    std::cout << x << std::endl;
  return 0;
}

该示例仅适用于不会使其无效的容器插入时的迭代器。我应该简单地摆脱迭代器和接受一个容器作为参数，还是我遗漏了一些关于insert_iterator 使这种用法成为可能？

Answer 1

The example works only for containers that do not invalidate their iterators on insertion.

没错。

Should I simply get rid of the iterators and accept a container as the argument

那是一种可能性。另一种方法是不就地制作算法(即输出到不同的容器/输出迭代器)。

am I missing something about insert_iterator that makes this kind of usage possible?

没有。 insert_iterator 用于重复插入到容器的单个位置，例如。通过变换算法。