dynamic array .length vs .reserve - what's the difference?
invalid at example.com
Thu Jul 30 15:58:28 UTC 2020
I just stumbled upon code like this:
b.length = n;
.reserve looks redundant.
The docs are explaining .length nicely, however lack any
specifics about reserve.
Changing the length of an array may relocate and copy. New items
are initialized with T.init - is that true for both length and
Also there's .capacity - is that equivalent to reserve ?
Another curiosity I noticed is that the docs say that the runtime
tries to resize in place, however:
b = b[0..$-1]; if length==1 seems to collect the memory at once
because if it's immediately followed by b.length = 1; or b ~=
someT; b.ptr points to a new address.
I know that b=b[0..0]; is equivalent to b = null; but I still
don't understand the need for a new allocation when b could be
resized in place.
How can I hold on to the memory originally reserved by b but at
the same time allow the array to temporarily be empty?
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