On 03/19/2011 10:05 AM, Mafi wrote:
> Am 19.03.2011 17:29, schrieb Piotr Szturmaj:
>> Shouldn't dynamic array be reference type?
> Just one note: appending (ar ~= 1) differs from concating (ar = ar ~ 1)
> that while the second is guanranteed to reallocate, about the first you
> can't be sure. It depends on the GC.
On the other hand, if the dynamic array is sharing a part of another
array, extending the dynamic array always breaks the sharing and the
dynamic array is always relocated.
void main()
{
int[] a = [ 100, 200, 300 ];
// Three slices (aka dynamic arrays) to the first two elements
int[] s0 = a[0..2];
int[] s1 = a[0..2];
int[] s2 = a[0..2];
// They share the same first two elements
assert(s0.ptr == a.ptr);
assert(s1.ptr == a.ptr);
assert(s2.ptr == a.ptr);
// All of these operations break the sharing
++s0.length;
s1 ~= 42;
s2 = s2 ~ 43;
// Nothing happened to the original
assert(a == [ 100, 200, 300 ]);
// Because nobody is sharing anymore
assert(s0.ptr != a.ptr);
assert(s1.ptr != a.ptr);
assert(s1.ptr != s0.ptr);
assert(s2.ptr != a.ptr);
assert(s2.ptr != s0.ptr);
assert(s2.ptr != s1.ptr);
}
I forgot the name of the feature. Basically, no slice (aka dynamic
array) can extend into other elements and starts sharing them.
Ali
