# std::ranges::chunk_view<V>::outer-iterator

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< cpp‎ | ranges‎ | chunk view

class /*outer-iterator*/ |  | (since C++23)

The return type of `chunk_view::begin` if `V` models `input_range`.

The name of this class (shown here as /*outer-iterator*/) is unspecified.

### Data members

Typical implementations of /*outer-iterator*/ hold only one non-static data member – a pointer `parent_` (the name is for exposition purposes only) to the "parent object", of type ranges::chunk_view*.

### Member types

Member type | Definition
`iterator_concept` | std::input_iterator_tag
`difference_type` | ranges::range_difference_t<V>

### Member functions

(constructor) (C++23) | constructs an iterator (public member function)
operator= (C++23) | move assigns another iterator (public member function)
operator* (C++23) | accesses the element (public member function)
operator++ (C++23) | increments the iterator (public member function)

### Non-member functions

operator== (C++23) | compares the iterator with default sentinel (function)
operator- (C++23) | calculates the number of chunks remaining (function)

### Nested classes

value_type (C++23) | the value type of /*output-iterator*/ (public member class)

### Example

A link to Compiler Explorer

Run this code

    #include <iostream>
    #include <iterator>
    #include <sstream>
    #include <ranges>

    int main()
    {
        const std::string source{"ABCDEFGHIJ"};

        auto letters = std::istringstream{source};
        auto chunks = std::ranges::istream_view<char>(letters)
                    | std::views::chunk(4);

        for (auto outer_iter = chunks.begin(); outer_iter != std::default_sentinel;
             ++outer_iter)
        {
            auto chunk = *outer_iter; // chunk is an object of type
                                      // chunk_view::outer_iterator::value_type
            std::cout << '[';
            for (auto inner_iter = chunk.begin(); inner_iter != std::default_sentinel;
                 ++inner_iter)
                std::cout << *inner_iter;
            std::cout << "] ";
        }
        std::cout << '\n';

        // The same output using range-for loops
        auto letters2 = std::istringstream{source};
        auto chunks2 = std::ranges::istream_view<char>(letters2)
                     | std::views::chunk(4);
        for (auto chunk : chunks2)
        {
            std::cout << '[';
            for (auto ch : chunk)
                std::cout << ch;
            std::cout << "] ";
        }
        std::cout << '\n';
    }

Output:

    [ABCD] [EFGH] [IJ]
    [ABCD] [EFGH] [IJ]

### References

- C++23 standard (ISO/IEC 14882:2023):

  - 26.7.28.3 Class `chunk_view::outer-iterator` [range.chunk.outer.iter]

### See also

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