标准库里的move()、move_backward()函数

使用一个东西，不明白它的道理，不高明
——侯捷老师

1.move()

功能:将一个序列里的元素移动到另一个序列里。

1.1 函数声明

template 
  OutputIterator move (InputIterator first, InputIterator last, OutputIterator result);

1.2 等价操作实现

template 
  OutputIterator move (InputIterator first, InputIterator last, OutputIterator result) {
    while (first != last) {
      *result = std::move(*first);
      ++result;
      ++first;
  }
  return result;
}

1.3 示例程式

void test_move() {
        std::vector foo = {"air","water","fire","earth"};
        std::vector bar (4);

        // moving ranges:
        std::cout << "Moving ranges...\n";
        std::move ( foo.begin(), foo.begin()+4, bar.begin() );

        std::cout << "foo contains " << foo.size() << " elements:";
        std::cout << " (each in an unspecified but valid state)";
        std::cout << '\n';

        std::cout << "bar contains " << bar.size() << " elements:";
        for (std::string& x: bar) std::cout << " [" << x << "]";
        std::cout << '\n';

        // moving container:
        std::cout << "Moving container...\n";
        foo = std::move (bar);

        std::cout << "foo contains " << foo.size() << " elements:";
        for (std::string& x: foo) std::cout << " [" << x << "]";
        std::cout << '\n';

        std::cout << "bar is in an unspecified but valid state";
        std::cout << '\n';
    }

1.4 参考链接

http://www.cplusplus.com/reference/algorithm/move/

2. move_backward()函数

2.1 函数声明

template 
  BidirectionalIterator2 move_backward (BidirectionalIterator1 first,
                                        BidirectionalIterator1 last,
                                        BidirectionalIterator2 result);

2.2等价操作实现

template
  BidirectionalIterator2 move_backward ( BidirectionalIterator1 first,
                                         BidirectionalIterator1 last,
                                         BidirectionalIterator2 result )
{
  while (last!=first) *(--result) = std::move(*(--last));
  return result;
}

2.3示例程式

void test_move_forward() {
        std::string elems[10] = {"air", "water", "fire", "earth"};
        string strs[5];

        // insert new element at the begining
        std::move_backward(elems, elems+4, strs+4);

        std::cout <<  strs[0] << endl;
        std::cout << "strs contains: ";
        for (auto& x : strs) {
            cout << x << " ";
        }
        cout << endl;

        for (int i = 0; i < 5; i++) {
            cout << i << " " << strs[i] << " ";
        }
        cout << endl;
    }

输出结果：
air
strs contains: air water fire earth
0 air 1 water 2 fire 3 earth 4

2.3 参考链接

http://www.cplusplus.com/reference/algorithm/move_backward/?kw=move_backward