Return static fixed size array from a function

Question

Is it possible to return a static fixed size array from a function? What would be the syntax for this. I am not asking for std::array, neither for T*, I am specifically asking for arrays of the form T arr[N]. For instance one can take such an array as an argument in a function through the following syntax:

template<typename T, auto N>
void func(T (&arr)[N])
{

}

Not entirely certain what you are asking, but If the array is scoped within the function, as in void func() { T arr[N]; }, it is dead at the end of the function. — user4581301
– user4581301, Commented Jul 6, 2019 at 0:56
@user4581301 I want to treat it like an object and return a copy (possibly with copy elision). Is this infeasible? — lightxbulb
– lightxbulb, Commented Jul 6, 2019 at 0:59
You return the array, it decays to a pointer and expires. Pretty much the only way to get one out is to wrap it in a a class, and if you're going to do that, ta-dah, poor-man's std::array. — user4581301
– user4581301, Commented Jul 6, 2019 at 1:03

Brian Bi · Accepted Answer · 2019-07-06 01:04:29Z

2

A function cannot return an array by value. You have observed that a function can take an array as an argument by reference; similarly a function can return an array by reference. To do so, it would be easiest to use the trailing return type syntax:

auto func() -> T (&)[N];

But arrays can be neither passed nor returned by value.

answered Jul 6, 2019 at 1:04

Brian Bi

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2 Comments

lightxbulb Over a year ago

This answers my question more than adequately. What is the reason as to why T(&)[N] cannot be at the place of the return type directly and but auto is necessary (I tried it, it didn't work)?

Brian Bi Over a year ago

@lightxbulb It can be done, but most people get the syntax wrong. coliru.stacked-crooked.com/a/ce8c356e17c9a2f4

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