在boost元组，zip_iterator等上使用std :: get和std :: tie [英] Using std::get and std::tie on boost tuples, zip_iterator, etc

问题描述

将std::get<>()和std::tie<>()与boost结构一起使用时，我有哪些选择?

What are my options for using std::get<>() and std::tie<>() together with boost constructs?

示例: 我想使用基于范围的for循环在多个容器上进行迭代.我可以实现使用boost::zip_iterator的zip函数.

Example: I want to use range-based for-loop for iteration over several containers. I can implement zip function, which uses boost::zip_iterator.

 #include <boost/iterator/zip_iterator.hpp>
 #include <boost/range.hpp>

 template <typename... TContainer>
 auto zip(TContainer&... containers) -> boost::iterator_range<boost::zip_iterator<decltype(boost::make_tuple(std::begin(containers)...))>> {
    auto zip_begin = boost::make_zip_iterator(boost::make_tuple(std::begin(containers)...));
    auto zip_end = boost::make_zip_iterator(boost::make_tuple(std::end(containers)...));
    return boost::make_iterator_range(zip_begin, zip_end);
 }

现在我可以像这样使用它:

Now I can use it like this:

std:list<int> a;
std::vector<double> b;
...
for (auto t : zip(a, b)) {
   // access elements by boost::get<0>(t), boost::get<1>(t)
   // or use boost::tie(a_element, b_element)
}

当我调用其他方法(期望是std::tuple或std::pair-我必须转换)时会出现问题，因为其余代码使用std::tuples，或者模板化代码使用std::get<>()和/或std::tie().

Problems occur when I call some other method, which expects std::tuple or std::pair - I have to convert), since rest of the code uses std::tuples, or when templated code uses std::get<>() and/or std::tie().

我发现一些补丁添加了对zip_iterator的std::tuple支持，但是在我的版本中未应用(我使用Boost 1.54).

I found some patches which add std::tuple support for zip_iterator, but these are not applied in my version (I use Boost 1.54).

我错过了什么吗?强制zip_iterator返回std::tuple或使std::get，std::tie等可用于增强类型的方法是什么?

Am I missing something? What are my options to either force zip_iterator to return std::tuple or make std::get, std::tie, etc. available for boost types?

推荐答案

在增强> = 1.55中使用boost::combine.

use boost::combine in boost >= 1.55.

for (auto a_tuple: boost::combine(va, vb)) {...} 或

for (auto a_tuple: boost::combine(va, vb)) {...} or

BOOST_FOREACH(boost::tie(elem_a, elem_b), boost::combine(va, vb)) {...}

BOOST_FOREACH(boost::tie(elem_a, elem_b), boost::combine(va, vb)) {...}

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