Is there a way to use a range defined with disabled post-blit in foreach? In other words, is there a way to prevent foreach from copying the range?

Should I use move()?

On 08/30/2016 12:06 PM, Yuxuan Shui wrote:
> Is there a way to use a range defined with disabled post-blit in
> foreach? In other words, is there a way to prevent foreach from copying
> the range?

It's not possible. You can't do much with such a range anyway. For example, even r.take(10) requires to copy.

Why do you want to prevent copying? There may be other ways around the issue.

> Should I use move()?

I don't know but I guess you can have a member function to do that.

Ali

On Tuesday, 30 August 2016 at 19:06:46 UTC, Yuxuan Shui wrote:
> Is there a way to use a range defined with disabled post-blit in foreach? In other words, is there a way to prevent foreach from copying the range?
>
> Should I use move()?
国人？望加群：531010036 谢谢

On Tuesday, 30 August 2016 at 20:30:12 UTC, Ali Çehreli wrote:
> On 08/30/2016 12:06 PM, Yuxuan Shui wrote:
>> Is there a way to use a range defined with disabled post-blit in
>> foreach? In other words, is there a way to prevent foreach from copying
>> the range?
>
> It's not possible. You can't do much with such a range anyway. For example, even r.take(10) requires to copy.
>
> Why do you want to prevent copying? There may be other ways around the issue.

I want to make a hash table that uses std.experiment.allocator. The bucket is allocated from an allocator, and freed in ~this(). I don't want to copy the whole bucket in this(this).

Maybe I should use a reference counter or something?

>
>> Should I use move()?
>
> I don't know but I guess you can have a member function to do that.
>
> Ali

On Wednesday, 31 August 2016 at 14:03:20 UTC, Yuxuan Shui wrote:
> I want to make a hash table that uses std.experiment.allocator. The bucket is allocated from an allocator, and freed in ~this(). I don't want to copy the whole bucket in this(this).
>
> Maybe I should use a reference counter or something?
>

A reference counter should solve the problem, but there's also the option of just making it a class instead of a struct

On 08/31/2016 07:03 AM, Yuxuan Shui wrote:

> I want to make a hash table that uses
> std.experiment.allocator. The bucket is allocated from an
> allocator, and freed in ~this(). I don't want to copy the whole
> bucket in this(this).

It sounds like you are conflating the concept of a container with the concept of a range. The range should be separate from the container and should be cheap to copy.

Ali

On Wednesday, 31 August 2016 at 18:28:20 UTC, Ali Çehreli wrote:
> On 08/31/2016 07:03 AM, Yuxuan Shui wrote:
>
> > I want to make a hash table that uses
> > std.experiment.allocator. The bucket is allocated from an
> > allocator, and freed in ~this(). I don't want to copy the
> whole
> > bucket in this(this).
>
> It sounds like you are conflating the concept of a container with the concept of a range. The range should be separate from the container and should be cheap to copy.
>
> Ali

OK, this would work for cases like containers. But what if I represent buffered network input as a range (like File.byLine), and I don't want to copy the buffer all the time? Any suggestion on how to do that correctly?

On Wednesday, 31 August 2016 at 23:38:21 UTC, Yuxuan Shui wrote:

>
> OK, this would work for cases like containers. But what if I represent buffered network input as a range (like File.byLine), and I don't want to copy the buffer all the time? Any suggestion on how to do that correctly?

Then the range should be constructed with a slice of the buffer if it's an array or with something pointer-based if it isn't (which requires a bit of bookkeeping). Ranges should be lightweight and should never require copying of the underlying data.