CODEWITHSUNDEEP
c++c++20range-v3
NicholasM
NicholasM

Reputation: 4673

In ranges-v3, how do I create a range from a pair of iterators?

How do I create a ranges-v3-compatible range, given a traditional pair of "begin" and "end" iterators?

Let's say that I am writing a generic function that accepts two iterators, for compatibility with legacy code.

struct result;  

bool keep_line(const std::string&);
result parse_line(const std::string&);

template <typename InputIt>
std::vector<result> parse_lines(InputIt begin, InputIt end)
{
    // This is what I want to do...
    auto lines = ranges::make_range_out_of_legacy_iterators(begin, end);

    return lines 
        | ranges::view::filter(keep_line) 
        | ranges::view::transform(parse_line) 
        | ranges::to<std::vector<result>>();
}

Upvotes: 15

Views: 4824

Answers (1)

NicholasM
NicholasM

Reputation: 4673

To create a range from a pair of iterators in ranges-v3, use the subrange view:

#include <range/view/subrange.hpp>

auto lines = ranges::subrange(begin, end);       // Requires C++17-style deduction

auto lines = ranges::make_subrange(begin, end);  // If template deduction not available

In old versions of the library, the iterator_range class in range/v3/iterator_range.hpp was apparently used, but that header is marked deprecated in the current ranges-v3 release (0.9.1).

Upvotes: 17

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