On 17.11.2015 20:46, maik klein wrote:
.selectFromTuple!(0, 1).expand
Does this result in a copy? I avoided doing it like this because I was
worried that I would copy every array. But I also don't fully understand
when D will copy.
Yes and no. It copies the Array structs, but it does not copy the
elements of the arrays. If I remember correctly, std.container.Array
uses reference counting, and copying them should be cheap.
By the way, do you have a good reason to go with Array!int rather than
int[]? They're similar, but the builtin int[] may be easier to handle.
Also doing
foreach(e;range){
e[0] = 10;
e[1] = 10.0f;
writeln("element: ",e);
}
foreach(e;range){
writeln("element: ",e);
}
doesn't mutate the range at all.
You need to mark the `e` as `ref`: `foreach(ref e; range)`. Otherwise,
it's a copy of the element, and any changes to it are forgotten at the
end of the iteration.
But even with `ref` it doesn't work. Seems to be a bug in or a
limitation of `zip`. Works with `lockstep`:
----
auto ranges = integrals
.selectFromTuple!(0, 1).expand
.mapTuple!(a => a[]).expand;
auto range = ranges.zip;
import std.range: lockstep;
foreach(ref e0, ref e1; lockstep(ranges)){
e0 = 10;
e1 = 10.0f;
}
foreach(e;range){
writeln("element: ",e);
}
----
