1 //Static array slice: no capacity
2 int[4] sarray = [1, 2, 3, 4];
3 int[] slice = sarray[];
4 assert(sarray.capacity == 0);
5 //Appending to slice will reallocate to a new array
6 slice ~= 5;
7 assert(slice.capacity >= 5);
8
9 //Dynamic array slices
10 int[] a = [1, 2, 3, 4];
11 int[] b = a[1 .. $];
12 int[] c = a[1 .. $ - 1];
13 debug(SENTINEL) {} else // non-zero capacity very much depends on the array and GC implementation
14 {
15 assert(a.capacity != 0);
16 assert(a.capacity == b.capacity + 1); //both a and b share the same tail
17 }
18 assert(c.capacity == 0); //an append to c must relocate c.
The D Programming Language's Unofficial Docs
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(Property) Gets the current capacity of a slice. The capacity is the size that the slice can grow to before the underlying array must be reallocated or extended.
If an append must reallocate a slice with no possibility of extension, then 0 is returned. This happens when the slice references a static array, or if another slice references elements past the end of the current slice.
Note: The capacity of a slice may be impacted by operations on other slices.