• Gr8Ape (17/17) May 27 2015 I'm writing a program that handles lots of slices of larger
• Steven Schveighoffer (6/23) May 27 2015 Slices can't do this, because they have no idea about each other. So
• =?UTF-8?B?Ik3DoXJjaW8=?= Martins" (7/7) May 27 2015 On Wednesday, 27 May 2015 at 07:55:29 UTC, Gr8Ape wrote:

"Gr8Ape" <bbgun turtles.net> writes:

I'm writing a program that handles lots of slices of larger
arrays. I need the data of each of them all together for one
operation, but otherwise it's more convenient to handle the
elements in small groups. I could just store a pointer to my
array, an offset, and a length but since I'm using D I'd much
prefer to use slices...

So I was looking through the documentation on slices and found
out that if the array has to realocate then slices pointing to
that array will keep on pointing to that block of memory, rather
than the new location. Given that I'll be working with arrays
that can vary wildly in size and that giving all of them the
maximum capacity so they never realocate would be extremely
inefficent, I need a workaround.

So I'm wondering if there's a way to tell all the slices of an
underlying array to now point to the new underlying array upon
reallocation? Or would I have to iterate through and reassign
every slice?

Steven Schveighoffer <schveiguy yahoo.com> writes:

On 5/27/15 1:55 AM, Gr8Ape wrote:
 I'm writing a program that handles lots of slices of larger
 arrays. I need the data of each of them all together for one
 operation, but otherwise it's more convenient to handle the
 elements in small groups. I could just store a pointer to my
 array, an offset, and a length but since I'm using D I'd much
 prefer to use slices...

 So I was looking through the documentation on slices and found
 out that if the array has to realocate then slices pointing to
 that array will keep on pointing to that block of memory, rather
 than the new location. Given that I'll be working with arrays
 that can vary wildly in size and that giving all of them the
 maximum capacity so they never realocate would be extremely
 inefficent, I need a workaround.

 So I'm wondering if there's a way to tell all the slices of an
 underlying array to now point to the new underlying array upon
 reallocation? Or would I have to iterate through and reassign
 every slice?

Slices can't do this, because they have no idea about each other. So 
when you append to one slice, you can't have it update all other 
relevant slices.

However, you could create a type that does this.

-Steve

=?UTF-8?B?Ik3DoXJjaW8=?= Martins" <marcioapm gmail.com> writes:

On Wednesday, 27 May 2015 at 07:55:29 UTC, Gr8Ape wrote:

You can keep an index and a count instead of a slice.
If you know your data well, you can exploit this knowledge, and 
this has the potential to save you many bytes per "slice" when 
dealing with large data sets.
Depending on your access patterns, it also has the potential to 
be fairly more cpu-efficient.