What type is 'double x[]' in c++?

Asked Jan 05 '21 at 21:17

Active Jan 05 '21 at 21:21

Viewed 53 times

I am working with a piece of code that creates a data structure and puts in it 2 values. It looks like this:

void func() {
    double x[] = {y, z};
}

What is the type of the object x? I am trying to return it from a function, so I need to specify the type.

I tried this, but it breaks with error: no viable overload '='

double func() {
    double x[] = {y, z};

    return x;
}

edited Jan 05 '21 at 21:21

Random Davis

asked Jan 05 '21 at 21:17

connor449

By "structure" do you mean "type"? – Random Davis Jan 05 '21 at 21:19
2

`x` is an array of `2` `double`, the type is `double[2]`, but you cannot return that from the function. – mch Jan 05 '21 at 21:19
@RandomDavis yes, sorry. – connor449 Jan 05 '21 at 21:20
You may or may not have trouble with this, as arrays are only sometimes copiable. – Mooing Duck Jan 05 '21 at 21:21
1

Try `std::array` – Ben Voigt Jan 05 '21 at 21:22
6

Sounds like you could use a [good C++ book](http://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list). In it they will go over arrays and how you can use them. – NathanOliver Jan 05 '21 at 21:22
1

@ThomasSablik: You can... and it would be wrong (the return type would be inferred as `double*`, a dangling pointer to a no-longer existing object). Demo: https://rextester.com/BDSP1549 – Ben Voigt Jan 05 '21 at 21:25
You cannot "return" this array, no matter what it's type is, from the function. Any attempt to do so will only end in tears. – Sam Varshavchik Jan 05 '21 at 21:26
@SamVarshavchik: You can return it as `std::array` just fine (maybe with help from `std::to_array()`. – Ben Voigt Jan 05 '21 at 21:28
An alternative is to place the array into a `struct` and pass the struct by reference to the function. – Thomas Matthews Jan 05 '21 at 21:39

0 Answers0