Simplest way to assign std::span to std::vector

Question

I wanted to do this

#include <vector>
#include <span>

struct S
{
    std::vector<int> v;
    void set(std::span<int> _v)
    {
        v = _v;
    }
};

But it does not compile. What are the alternatives?

score 15 · Accepted Answer · answered Sep 01 '20 at 10:49

15

v.assign(_v.begin(), _v.end());

answered Sep 01 '20 at 10:49

yuri kilochek

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Thanks, pretty neat. I was thinking of doing clear() + insert() but this looks better. – tuket Sep 01 '20 at 10:59
that (`clear` + `insert`) is basically what `assign` does. – Marshall Clow Sep 01 '20 at 14:26
admittedly the `clear` is extra if its in the constructor as you wouldn't expect the any data elements in an empty vector. – Mikhail Aug 01 '22 at 02:08

score 3 · Answer 2 · answered Sep 01 '20 at 12:26

You can also use the std::vector::insert as follows:

v.insert(v.begin(), _v.begin(), _v.end());

Note that, if the v should be emptied before, you should call v.clear() before this. However, this allows you to add the span to a specified location in the v.

(See a demo)

Simplest way to assign std::span to std::vector

2 Answers2