After a discussion on digitalmars.D I played with arrays a bit. Look at the
following code:
int[] a = [1,2,3,4,5,6,7,8,9] ;
int[] b = a ;
a ~= 10 ;
b ~= 11 ;
b[0] = 12 ;
Stdout(b).newline ;
Stdout(a).newline ;
The result is:
[12, 2, 3, 4, 5, 6, 7, 8, 9, 11]
[12, 2, 3, 4, 5, 6, 7, 8, 9, 11]
Which means that even though b was set only to a[0..10], after expanding b,
also has direct access to element a[10]. But
int[] a = [1,2,3,4,5,6,7,8,9] ;
int[] b = a ;
a ~= 10 ;
b.length = b.length+1 ;
b[0] = 11 ;
Stdout(b).newline ;
Stdout(a).newline ;
Gives
[11, 2, 3, 4, 5, 6, 7, 8, 9, 0]
[11, 2, 3, 4, 5, 6, 7, 8, 9, 0]
Now b is expanded in length, but a side effect is that a[10] is set to 0 (i.e.
initialized).
In the end, I think b can only see things that happen to a[10] after it
expanded, but not before. It seems there is no way for the following to work:
int[] a = [1,2,3,4,5,6,7,8,9] ;
int[] b = a ;
a ~= 10 ;
At this point, element a[10]=10 will never be visible to b. b can expand to it,
but by doing that, a[10] will be overwritten.
Is this on purpose? It could also be useful to have b.length=b.length+1 which
only initializes memory that has not been initialized before.
