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digitalmars.D.learn - Prevent copy of range in foreach

reply Yuxuan Shui <yshuiv7 gmail.com> writes:
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()?
Aug 30 2016
next sibling parent reply =?UTF-8?Q?Ali_=c3=87ehreli?= <acehreli yahoo.com> writes:
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
Aug 30 2016
parent reply Yuxuan Shui <yshuiv7 gmail.com> writes:
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
Aug 31 2016
next sibling parent pineapple <meapineapple gmail.com> writes:
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
Aug 31 2016
prev sibling parent reply =?UTF-8?Q?Ali_=c3=87ehreli?= <acehreli yahoo.com> writes:
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
Aug 31 2016
parent reply Yuxuan Shui <yshuiv7 gmail.com> writes:
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?
Aug 31 2016
parent Mike Parker <aldacron gmail.com> writes:
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.
Aug 31 2016
prev sibling parent mogu <mogucpp 163.com> writes:
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
Aug 31 2016