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digitalmars.D.learn - Double ended arrays?

reply Chirs Forest <CF chrisforest.com> writes:
I have some data that I want to store in a dynamic 2d array... 
I'd like to be able to add elements to the front of the array and 
access those elements with negative integers as well as add 
numbers to the back that I'd acess normally with positive 
integers. Is this something I can do, or do I have to build a 
container to handle what I want?
Oct 07 2017
next sibling parent Ilya Yaroshenko <ilyayaroshenko gmail.com> writes:
On Saturday, 7 October 2017 at 07:38:47 UTC, Chirs Forest wrote:

 I have some data that I want to store in a dynamic 2d array... 
 I'd like to be able to add elements to the front of the array 
 and access those elements with negative integers as well as add 
 numbers to the back that I'd acess normally with positive 
 integers. Is this something I can do, or do I have to build a 
 container to handle what I want?


Mir Algorithm [1] has 2D arrays. Elements can be added to the 
front/back of each dimension using `concatenation` routine [2]. 
In the same time it does not support negative indexes.

[1] https://github.com/libmir/mir-algorithm

[2] 


Best regards,
Ilya Yaroshenko
Oct 07 2017
prev sibling next sibling parent Jonathan M Davis <newsgroup.d jmdavisprog.com> writes:
On Saturday, October 07, 2017 07:38:47 Chirs Forest via Digitalmars-d-learn 
wrote:

 I have some data that I want to store in a dynamic 2d array...
 I'd like to be able to add elements to the front of the array and
 access those elements with negative integers as well as add
 numbers to the back that I'd acess normally with positive
 integers. Is this something I can do, or do I have to build a
 container to handle what I want?


Dynamic arrays only support concatenating to the end, and they use size_t
for indices and length, and size_t is unsigned. The standard library does
the same with any containers that it has as do most 3rd party libraries.

You'll need to either implement what you want yourself or use something from
somewhere like code.dlang.org. Based on Ilya's post, it sounds like you may
be able to use Mir for what you want, but I'd be very surprised to see any
libraries use negative indices for anything - especially since most
everything uses size_t for indices.

- Jonathan M Davis
Oct 07 2017
prev sibling parent reply Steven Schveighoffer <schveiguy yahoo.com> writes:
On 10/7/17 3:38 AM, Chirs Forest wrote:

 I have some data that I want to store in a dynamic 2d array... I'd like 
 to be able to add elements to the front of the array and access those 
 elements with negative integers as well as add numbers to the back that 
 I'd acess normally with positive integers. Is this something I can do, 
 or do I have to build a container to handle what I want?


Dcollections has something like this, a deque. It doesn't use negative 
integers to access the prepended elements, but I suppose it could be 
made to do this.

See here:

https://github.com/schveiguy/dcollections/blob/master/dcollections/Deque.d

It's implemented by maintaining 2 dynamic arrays, one that is "reversed" 
at the front, and one that is normal at the back. When you prepend, it 
appends to the "reverse" array.

It's probably not the most efficient, but it does maintain the correct 
complexities.

Note: that code is many years old, so it may not compile with the latest 
compiler.

-Steve
Oct 07 2017
parent =?UTF-8?Q?Ali_=c3=87ehreli?= <acehreli yahoo.com> writes:
On 10/07/2017 05:02 PM, Steven Schveighoffer wrote:


 


https://github.com/schveiguy/dcollections/blob/master/dcollections/Deque.d

 It's implemented by maintaining 2 dynamic arrays, one that is "reversed"
 at the front, and one that is normal at the back. When you prepend, it
 appends to the "reverse" array.

 It's probably not the most efficient, but it does maintain the correct
 complexities.


I stole the idea from one of Chuck Allison's DConf talks[1] and used as 
the example for the Indexing Operators section here:

 
http://ddili.org/ders/d.en/operator_overloading.html#ix_operator_overloading.opIndex


 Note: that code is many years old, so it may not compile with the latest
 compiler.


Mine is supposed to compile with 2.076.


 -Steve


Ali

[1] He knows about the theft. :)
Oct 07 2017