List subsequences

[weak swallow]

In Python there is something like this: list[1:3] that returns the subsequence of the list including the second and third element. What is its equivalence in C++?

[round narwhal]

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cppreference.com

std::ranges::subrange

template<
    std::input_or_output_iterator I,
    std::sentinel_for<I> S = I,
    ranges::subrange_kind K =
        std::sized_sentinel_for<S, I>
            ? ranges::subrange_kind::sized
            : ranges::subrange_kind::unsized>
requires(
    K == ranges::subrange_kind::sized ||
    !std::
        sized_sentinel_for<S, I>) class subrange
    : public ranges::view_interface<
          subrange<I, S, K>>

Defined in

<ranges>

[winter quail]

But that’s kinda advanced

Some containers have built in functions to do this, like std::string

[spiral swift]

The equivalent in C++ is an iterator pair (a lot of functions like std::sort or constructors for std::vector take a begin and end iterator). Newer version pack iterator pairs into ranges: https://en.cppreference.com/w/cpp/ranges/range

It really depends on what you want to do with the sublist. std::vector sublist(std::begin(v) + 1, std::begin(v) + 3); is more or less equivalent to the Python code, but usually you want to avoid copies.

[hot dagger]

since C++20, you could pack the subrange into a std::span

[round narwhal]

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