How to assign multiple values to an array?

Question

I can declare and initialize an array like this:

int dest_linesize[4] = {  4 , 0 , 0 , 0 };

I can always assign values to the individual members of the array by:

dest_linesize[0] = 5;

But can I assign multiple values with something like this?

dest_linesize = {  4 , 3 , 1 , 0 };

Yksisarvinen · Accepted Answer · 2020-07-23 11:45:59Z

2

With C-style array? No, they are not reassignable.

With C++ std::array? Sure

#include <array>
int main()
{
    std::array<int, 4> dest_linesize = {4 , 0 , 0 , 0 };
    dest_linesize[0] = 5;
    for(int n:dest_linesize) {
        std::cout << n << " ";
    }
    std::cout << "\n";

    dest_linesize = {  4 , 3 , 1 , 0 };
    for(int n:dest_linesize) {
        std::cout << n << " ";
    }
}

answered Jul 23, 2020 at 11:45

Yksisarvinen

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2 Comments

shomit Over a year ago

if i have to pass a c style array to a function how can i pass the std::array ?

Yksisarvinen Over a year ago

@shomit If you can't change that function, dest_linesize.data() will extract the underlying array.

eerorika · Accepted Answer · 2020-07-23 11:47:01Z

2

can i do something like this instead where i can assign multiple values.
dest_linesize = {  4 , 3 , 1 , 0 };

No, you cannot. Arrays are not assignable.

One solution is to wrap the array inside a class. Classes are assignable. There is a template for such wrapper in the standard library. It is called std::array. Example:

std::array dest_linesize = {  4 , 0 , 0 , 0 };
dest_linesize = {  4 , 3 , 1 , 0 }

answered Jul 23, 2020 at 11:47

eerorika

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