On Wednesday, 1 June 2016 at 14:52:29 UTC, John Nixon wrote:
On Wednesday, 2 March 2016 at 21:37:56 UTC, Steven
Schveighoffer wrote:
Pointer copying is inherent in D. Everything is done at the
"head", deep copies are never implicit. This is a C-like
language, so one must expect this kind of behavior and plan
for it.
I sympathise with Ozan. What is the best reference you know
that explains this fully?
Slices/dynamic arrays are literally just a pointer (arr.ptr) and
a length (arr.length).
Assigning a slice simply copies the ptr and length fields,
causing the slice to refer to the entire section of data. Slicing
(arr[1..2]) returns a new slice with the ptr and length fields
updated.
(This also means you can slice arbitrary pointers; ex.
`(cast(ubyte*) malloc(1024))[0..1024]` to get a slice of memory
backed by C malloc. Very useful.)
The only magic happens when increasing the size of the array, via
appending or setting length, which usually allocates a new array
from the GC heap, except when D determines that it can get away
with not doing so (i.e. when the data points somewhere in a GC
heap and there's no data in-use after the end of the array.
capacity also looks at GC metadata).
