On Thursday, 17 October 2013 at 18:29:47 UTC, John Colvin wrote:
On Thursday, 17 October 2013 at 18:00:20 UTC, Vitali wrote:
I expected slices to be in D (http://dlang.org/arrays.html)
like they are in Go
(http://blog.golang.org/go-slices-usage-and-internals). But
they are not.
Why the array have to be reallocated after the length of a
slice is changed? It makes slices useless.
Here a little example (it fails):
void testSlices() {
int[] dArr = [10, 11, 12];
int[] dSlice = dArr[0..2];
dSlice.length++;
assert(dArr[2]==dSlice[2]); // failure
}
What's the use case for this? I haven't found myself ever
needing something like that so far, but i'd be open to seeing
an example.
The use case is:
void appendElement(ref int[] arr, int x) {
arr ~= x;
}
void removeElement(ref int[] arr, int index) {
arr = arr[0..index] ~ arr[index+1..$];
}
void main() {
int[] arr = [1, 2, 3];
arr.reserve(7); // Reserve capacity.
arr.appendElement(4); // Here should be
arr.removeElement(1); // no realocation of array,
arr.appendElement(5); // but it is.
assert(arr[1] == 3);
assert(arr[2] == 4);
assert(arr[3] == 5);
}
But maybe I don't understand what slices are for in D. Anyway in
Go this works whithout reallocation.
