Decay std::array to pointer

Question

I have class like this:

struct S{
    void method1(int *a){
       // use a
    }

    void method2(int *a){
       // use a
    }
};

To avoid allocation, I am doing following:

std::array<int, 100> a;
S s;
s.method1(a.data());

However much nicer will be if I can able to do, without making all methods templates.

std::array<int, 100> a;
S s;
s.method1(a);

In C++20 I can use std::span, but currently I want to avoid it as well.

Any easy way to define some operator that will be able to convert / cast, but only inside the class?

One of the purposes of std::array is not to decay to a pointer. You may use int a[100] if you need the implicit array to pointer decay. — paolo
– paolo, Commented Sep 29, 2022 at 9:27
A side note: not sure it's a good idea to use std::array for a, as it will occupy ~400 bytes (assuming int is 4 bytes) on the stack which is quite a lot. — wohlstad
– wohlstad, Commented Sep 29, 2022 at 9:27
@paolo you are right. but I want something in between ;) I want to be able to return std::array from function and pass it, without specifying .data() every time. std::span is made exactly for this. — Nick
– Nick, Commented Sep 29, 2022 at 9:30

Quimby · Accepted Answer · 2022-09-29 09:36:34Z

5

You can use non-member std::data and call it like s.method1(std::data(a));.

That works for raw arrays, std::array, std::span and others.

answered Sep 29, 2022 at 9:36

Quimby

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