import std.stdio;
union EarthLocation
{
struct { immutable double lon, lat, alt; }
double[3] data;
}
void main()
{
EarthLocation d = {data: [4, 5, 6]};
writeln(d.data);
d.data = [1, 2, 3];
writeln(d.data);
}
I get the output:
[4, 5, 6]
[1, 2, 3]
I thought the promise of
On Saturday, 2 January 2016 at 12:07:31 UTC, John Colvin wrote:
You are manually breaking immutable by making a union of
immutable and mutable data and then writing to the mutable
reference. This is roughly equivalent to casting away immutable
and then writing to the reference. It's a bug in
On Saturday, 2 January 2016 at 10:04:47 UTC, Shriramana Sharma
wrote:
import std.stdio;
union EarthLocation
{
struct { immutable double lon, lat, alt; }
double[3] data;
}
void main()
{
EarthLocation d = {data: [4, 5, 6]};
writeln(d.data);
d.data = [1, 2, 3];
On Saturday, 2 January 2016 at 12:08:48 UTC, Meta wrote:
On Saturday, 2 January 2016 at 12:07:31 UTC, John Colvin wrote:
You are manually breaking immutable by making a union of
immutable and mutable data and then writing to the mutable
reference. This is roughly equivalent to casting away
On Saturday, 2 January 2016 at 12:08:48 UTC, Meta wrote:
On Saturday, 2 January 2016 at 12:07:31 UTC, John Colvin wrote:
You are manually breaking immutable by making a union of
immutable and mutable data and then writing to the mutable
reference. This is roughly equivalent to casting away
John Colvin wrote:
> Casting away immutable can sometimes be necessary (e.g. when
> talking to other languages), so I'm not sure it should be
> disallowed, but it'd be great if it was somehow easier to catch
> these bugs.
Yes it was in the context of talking to C that I needed to make such a
On Saturday, 2 January 2016 at 10:04:47 UTC, Shriramana Sharma
wrote:
I thought the promise of `immutable` was: never changes.
The compiler doesn't protect you by carrying a bomb. :)
But there is another usecase where it makes sense to allow
writing to other union members despite the
On Saturday, 2 January 2016 at 13:15:37 UTC, John Colvin wrote:
Casting away immutable can sometimes be necessary (e.g. when
talking to other languages), so I'm not sure it should be
disallowed, but it'd be great if it was somehow easier to catch
these bugs.
It should be disallowed in @safe
