Return std::array from a function as a range

Question

Say I have two arrays:

constexpr std::array<int, 3> a1{1, 2, 3};

constexpr std::array<int, 5> a2{1, 2, 3, 4, 5};

What is the right way to convert them to ranges of the same type to make it possible to call process_result function with their return values?

constexpr void process_result(RangeType range) { for (auto elem: range) { //do something with elem }

So the question is what is RangeType.

An obvious solution is to replace std::array with std::vector, but I wonder to know what to do with std::array.

Can we see how process_result(RangeType range); is declared/defined? You might not need to do anything as an array is already a range. — NathanOliver
– NathanOliver, Commented Sep 13, 2021 at 13:09
@NathanOliver It has a parameter of RangeType and it is non-template. — Dmitriano
– Dmitriano, Commented Sep 13, 2021 at 13:13
"An obvious solution is to replace std::array with std::vector". I don't see how it "defines" RangeType... — Jarod42
– Jarod42, Commented Sep 13, 2021 at 13:19

Jarod42 · Accepted Answer · 2021-09-13 13:24:43Z

4

You might use (non owning) std::span to allow any contiguous ranges:

constexpr void process_result(std::span<const int> range)
{
    for (auto elem: range) {
        //do something with elem
    }
}

answered Sep 13, 2021 at 13:24

Jarod42

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Comments

eerorika · Accepted Answer · 2021-09-13 14:05:42Z

1

If you don't necessarily need a function, and can instead use a function template, then you can make it more generic by supporting all ranges; not just contiguous ones:

constexpr void
process_result(const auto& range)
{
    for (const auto& elem: range) {
        //do something with elem
    }
}

answered Sep 13, 2021 at 14:05

eerorika

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