Welcome to OStack Knowledge Sharing Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
359 views
in Technique[技术] by (71.8m points)

c++14 - Is there an equivalent to the range-based `enumerate` loop from python in modern C++?

Is there an equivalent to the range-based enumerate loop from python in C++? I would imagine something like this.

enumerateLoop (auto counter, auto el, container) {
    charges.at(counter) = el[0];
    aa.at(counter) = el[1];
}

Can this be done with templates or macros?

I'm aware that I can just use an old school for-loop and iterate until I reach container.size(). But I'm interested how this would be solved using templates or macros.

EDIT

I played a bit with boost iterators after the hint in the comments. I got another working solution using C++14.

template <typename... T>
auto zip(const T &... 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);
}

template <typename T>
auto enumerate(const T &container) {
return zip(boost::counting_range(0, static_cast<int>(container.size())),
container);
} 

https://gist.github.com/kain88-de/fef962dc1c15437457a8

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Answer

0 votes
by (71.8m points)

Enumeration of multiple variables has been an idiom since C. The only complication is that you can't declare both variables in the initializer of the for loop.

int index;
for (auto p = container.begin(), index = 0; p != container.end(); ++p, ++index)

I don't think it gets any simpler (or more powerful) than that.


与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome to OStack Knowledge Sharing Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...