c - Why can't arrays of same type and size be assigned?

Question

If I declare two arrays - arr1 and arr2 - of, say, type int of size 10 each, and initialize first array, and I wish to create a copy of arr1 in arr2; why can't I just give the instruction arr2 = arr1 ?

I know two structures of same type can be assigned. Why is that not the case with arrays?

Answer 1

The problem with arrays is that in all expressions (except when passed to the sizeof and the unary & operators) they convert to a pointer to their first element.

So, supposing you have:

int arr1[10];
int arr2[10];
...

Then if you write something like

arr1 = arr2;

you are actually attempting to do this:

arr1 = &arr2[0];

or this:

&arr1[0] = &arr2[0];

In both cases you have a problem preventing your code from compiling. In the former case you're attempting to assign between two incompatible types (array vs pointer), while in the latter case you're attempting to modify a constant pointer (&arr1[0]).