www.digitalmars.com         C & C++   DMDScript  

digitalmars.D.learn - Removing elements from dynamic array

reply "Reflexive" <alexgyg msn.fr> writes:
Hi

I have seen that it is possible to remove an element from a 
associative array, but dont find any reference, including in D's 
specification, about any element removing in dynamic array. I can 
use loops for that, but isnt any way to simple reduce a dynamic 
array size ?

Thank you
Aug 09 2015
parent reply "cym13" <cpicard openmailbox.org> writes:
On Sunday, 9 August 2015 at 13:22:02 UTC, Reflexive wrote:

 Hi

 I have seen that it is possible to remove an element from a 
 associative array, but dont find any reference, including in 
 D's specification, about any element removing in dynamic array. 
 I can use loops for that, but isnt any way to simple reduce a 
 dynamic array size ?

 Thank you


You can use std.algorithm.remove for that. If you need more 
advanced ways to remove elements, you may want to switch from a 
regular dynamic array to a std.container.array.
Aug 09 2015
parent reply "Reflexive" <alexgyg msn.fr> writes:
On Sunday, 9 August 2015 at 13:40:51 UTC, cym13 wrote:

 On Sunday, 9 August 2015 at 13:22:02 UTC, Reflexive wrote:

 You can use std.algorithm.remove for that. If you need more 
 advanced ways to remove elements, you may want to switch from a 
 regular dynamic array to a std.container.array.


I get :

Error: module remove is in file 'std/algorithm/remove.d' which 
cannot be read
import path[0] = /usr/include/dmd/phobos
import path[1] = /usr/include/dmd/druntime/import

I'm in Linux Mint 17 ... maybe an permission problem ?
Aug 09 2015
next sibling parent Rikki Cattermole <alphaglosined gmail.com> writes:
On 10/08/2015 2:24 a.m., Reflexive wrote:

 On Sunday, 9 August 2015 at 13:40:51 UTC, cym13 wrote:

 On Sunday, 9 August 2015 at 13:22:02 UTC, Reflexive wrote:

 You can use std.algorithm.remove for that. If you need more advanced
 ways to remove elements, you may want to switch from a regular dynamic
 array to a std.container.array.


 I get :

 Error: module remove is in file 'std/algorithm/remove.d' which cannot be
 read
 import path[0] = /usr/include/dmd/phobos
 import path[1] = /usr/include/dmd/druntime/import

 I'm in Linux Mint 17 ... maybe an permission problem ?


You sure you are using it correctly (off top of my head)?

-----
import std.algorithm : remove;

...
arr.remove(e);

-----
Aug 09 2015
prev sibling parent reply "kinke" <noone nowhere.com> writes:
On Sunday, 9 August 2015 at 14:24:38 UTC, Reflexive wrote:

 Error: module remove is in file 'std/algorithm/remove.d' which 
 cannot be read


remove() is a function in module std.algorithm:

import std.algorithm: remove;
remove(foo);
Aug 09 2015
parent reply "Reflexive" <alexgyg msn.fr> writes:
I wrote import std.algorithm.remove ;, and I dont have any longer 
any error. But, it dont want to remove the item. Here is the 
source, the problem is in the shuffle() method :

// sabot.d
// version 0.0.1
import std.stdio ;
import std.random ;
import std.algorithm : remove ;


void main(){
	auto deck = new sabot ;
	deck.shuffle() ;

class sabot{
	card[] sabotarray ;

	(...)

	struct card {
		int id ;
		(...)
	}

	(...)

	this(){
		(the constructor builds up the array 'sabotarray'.)
}
	void shuffle(){
		card[] tempsabotarray ;
		card tempcard ;
		long id_card ;
		int counter ;
		while(this.sabotarray.length>1){
			if(counter>=60){break;}

			id_card = uniform(0,this.sabotarray.length-1) ;

			tempcard = this.sabotarray[id_card] ;
			this.sabotarray.remove(id_card) ;
			tempsabotarray ~= tempcard ;

			writeln ("Counter : " , counter, " ; id card : " , id_card, " 
; sabot size : ", this.sabotarray.length) ;
			++counter ;
		}
		this.sabotarray = tempsabotarray ;
	}

	(...)
}

And I get in the terminal :

$ dmd -run sabot.d
Counter : 0 ; id card : 18 ; sabot size : 52
Counter : 1 ; id card : 40 ; sabot size : 52
Counter : 2 ; id card : 14 ; sabot size : 52
Counter : 3 ; id card : 44 ; sabot size : 52
(...)

Until counter is 60. Sabot size remains 52 all the time.

Without the break statement, the computer goes out of memory.
Aug 09 2015
parent reply "Alex Parrill" <initrd.gz gmail.com> writes:
On Sunday, 9 August 2015 at 15:30:32 UTC, Reflexive wrote:

 I wrote import std.algorithm.remove ;, and I dont have any 
 longer any error. But, it dont want to remove the item. Here is 
 the source, the problem is in the shuffle() method :

 ...


Why not just use std.random.shuffle [1]?

     import std.random;

     void shuffle() {
         randomShuffle(this.sabotarray);
     }

(Also, this is more of a style opinion, but please don't define 
all your variables up front; define them when they're first used. 
The other way IMO has too much cognitive load, and you can't use 
`auto` in many cases)
Aug 09 2015
parent reply "Reflexive" <alexgyg msn.fr> writes:
On Sunday, 9 August 2015 at 15:41:33 UTC, Alex Parrill wrote:

 Why not just use std.random.shuffle [1]?


Well, I didn't knew about it, that's the reason ...

For the shuffle method, it is certainly the best to do, but I 
need the remove() method at other places. I see that remove() 
removes the value of the element but keeps the same size of the 
array, and replace the value by a new one at the end. The method :

class sabot{
	card[] sabotarray ;

	(...)

	card getCard(){
		card returncard = this.sabotarray[0] ;
		this.sabotarray.remove(0) ;
		return returncard ;
	}

The sabotarray before taking away cards :

$ dmd -run sabot.d
0. 🂡
1. 🂢
2. 🂣
...
48. 🃚
49. 🃛
50. 🃝
51. 🃞

The sabotarray after removing the two first cards :

$ dmd -run sabot.d
0. 🂣
1. 🂤
2. 🂥
...
47. 🃛
48. 🃝
49. 🃞
50. 🃞
51. 🃞
Aug 09 2015
next sibling parent "anonymous" <anonymous example.com> writes:
On Sunday, 9 August 2015 at 20:23:00 UTC, Reflexive wrote:

 I see that remove() removes the value of the element but keeps 
 the same size of the array, and replace the value by a new one 
 at the end. The method :

 class sabot{
 	card[] sabotarray ;

 	(...)

 	card getCard(){
 		card returncard = this.sabotarray[0] ;
 		this.sabotarray.remove(0) ;
 		return returncard ;
 	}


`remove` doesn't update the passed array, but it returns a slice 
of it that doesn't include the removed element. To update the 
original array, assign the result of `remove` to it:

this.sabotarray = this.sabotarray.remove(0);
Aug 09 2015
prev sibling parent reply drug <drug2004 bk.ru> writes:
09.08.2015 23:22, Reflexive пишет:


Try to use
this.sabotarray = this.sabotarray.remove(id_card);

remove() removes element(s) but doesn't change length of 'old' array. To 
get new length you should use 'new' array that returned from remove(). 
In this case I get rid of two excessive kings in cards.



 Aug 09 2015



  parent  "Reflexive" <alexgyg msn.fr>  writes:


On Sunday, 9 August 2015 at 20:38:05 UTC, drug wrote:

 09.08.2015 23:22, Reflexive пишет:


 Try to use
 this.sabotarray = this.sabotarray.remove(id_card);

 remove() removes element(s) but doesn't change length of 'old' 
 array. To get new length you should use 'new' array that 
 returned from remove(). In this case I get rid of two excessive 
 kings in cards.


Thank you to both anonymous and drug, that was the solution.



 Aug 09 2015