On 07/01/2013 10:34 AM, Damian wrote:
> void testref(ref int[] arr)
> {
> arr[0] = 1;
> }
>
> void test(int[] arr)
> {
> arr[0] = 1;
> }
>
> void main()
> {
> //int[] buffer1 = new int[4]; // This works
> int[4] buffer1; // This doesn't
> int[4] buffer2;
>
> testref(buffer1);
When that call is made, a slice would have to be created to represent
all of the elements of the fixed-length array buffer1. A slice would be
needed because buffer1 is not a slice but testref() takes a slice.
By the simplest definition, that slice is an rvalue because it is not
defined as a variable in the program.
And rvalues cannot be bound to non-const references. (If I am not
mistaken not even to const references yet, if ever.)
> test(buffer2);
Similarly, when that call is made, a slice is created. The difference
is, because the parameter is by-value, the slice gets copied to test().
Now there is no problem because 'arr' is just a local variable of test().
(Note that when I say a slice is created or a slice is copied, they are
very cheap operations. A slice is nothing but the number of elements and
a pointer to the first one of those elements. Just a size_t and a pointer.)
>
> assert(buffer1[0] == 1);
> assert(buffer2[0] == 1);
> }
>
> I'm not sure why my code doesn't work?? Isn't the buffer just an array
> with a fixed length? DMD is telling me 'buffer1 is not an lvalue'. The
> non ref version works fine?!
Ali
