Digital Workshop

I wonder how it is possible to remove/delete elements from an array.
Since I did not find such a command in the help files, I have already tried possible undocumented commands like splice or delete but without success.

Thanks in advance.

T.

Sorry T,

Opus Script is ECMA v1.1 and those Array methods don't exist. You can, with a bit of magic, add your own method and there are some posts on that around here somewhere or create just use the function bit.

Remember though that arrays are passed and assigned by reference.

Mack

... ouch ... I found out that there is also no possibility to copy arrays without the slice function. Since I am not a real programmer I would be glad if someone has an idea how to find a solution for this. How do you handle problems where lists are needed? In my case it's only a little game but I have no idea how to do this without lists so far.


T.



... I would like to do that but as mentioned above I am no real programmer and don't really know what you mean with your suggestion.

Something like this:



But note how inneficient it is. Arrays aren't a good choice if you need to remove things from the middle, you're better off using a linked list. It's okay for half a dozen elements, but if you have thousands the remove is going to be slow.

Dave,

thanks a lot for your help.



Since I like to learn (and besides that have actually a lot of items in this list): Would you be so kind to explain what you mean with "linked list". I have already searched the forum but could not find any information about this topic)

I'm not looking for a ready to use solution but like to understand how this works.

Thanks in advance

T.

They'd be in the Advanced+1 section

OpusScript doesn't have linked lists, you'd have to write your own - now there's a challenge - where's Lar?

As for what they are:

Image you have have three objects call them Dave, Mack and Tarantoga. To get from Dave to Tarantoga you have to go through Mack much in the same way as you do with Arrays. Except with linked lists the way you navigate through the list is by querying each object.

IE, you ask Dave who is before him and he replies -'nobody' - you ask him who is after him and he replies - 'Mack'

Do the same with Mack and he replies that Dave is before him and Tarantoga is after him.

Now if you want to remove Mack from this (great idea at this point) and rather than move everybody down the list (there could be every forum member after Tarantogo in this list) you simply tell Dave that Tarantoga is after him and tell Tarantoga that Dave is before him and Mack has gone!

You need to use objects, rather than variables, because each list items needs three bits of information, the value held, the object before and the object after.

Mack

Tar,

Can you give some idea of the scope here?
How large is the array? Array or arrays?
How do you identify which array element to delete? By content or by index?

I have an idea for creating a 'mask'... may serve your purpose to filter out elements. Then again, whether this is practical and efficient depends on your next steps and methods after getting the modified array.

What's wrong with using the built in "delete"?

/*******************************************/
arr = new Array("A","B","C");
delete arr[0];
// removes "A" from the array...
Debug.trace(arr);
/*******************************************/

Paul

Surely it hasn't actually gone - just become undefined?



Mack

Hi Mack,
Yes... Just checked my notes...
Definitely "Undefined" using the script below:

/*****************************************/
arr = new Array("A","B","C");
delete arr[0];

var i;
display="";
for (var i = 0; i <= arr.length-1; i++)
display = display + (arr[i] + "\n" );
Debug.trace(display)
/*****************************************/


So I'd probably use something like:

/**********************************************************/

// define method
function arrayRemove(n){
if (!n) return;
var i, l = this.length;
for (i=n+1; i < l; i++)
this[i-1] = this[i];
this.length--;
}

if (typeof(Array.prototype.remove) == "undefined") {
Array.prototype.remove = arrayRemove;
}

// usage
// create array
var a1 = new Array("a","b","c","d");

Debug.trace("Initial array is "+a1+"\n")
Debug.trace("remove third element 'c' from array a1 with a1.remove(2)"+"\n")
a1.remove(2);
Debug.trace("new array is "+a1)

/******************************************************/


Paul