Arrays - Inserting and moving data

[MattCodr]

On Thursday, 9 February 2012 at 18:30:22 UTC, Ali Çehreli wrote:
> On 02/09/2012 03:47 AM, MattCodr wrote:
>> I have a doubt about the best way to insert and move (not 
>> replace) some
>> data on an array.
>>
>> For example,
>>
>> In some cases if I want to do action above, I do a loop moving 
>> the data
>> until the point that I want and finally I insert the new data 
>> there.
>>
>>
>> In D I did this:
>>
>> begin code
>> .
>> .
>> .
>> int[] arr = [0,1,2,3,4,5,6,7,8,9];
>>
>> arr.insertInPlace(position, newValue);
>> arr.popBack();
>> .
>> .
>> .
>> end code
>>
>>
>> After the insertInPlace my array changed it's length to 11, so 
>> I use
>> arr.popBack(); to keep the array length = 10;
>>
>> The code above is working well, I just want know if is there a 
>> better way?
>>
>> Thanks,
>>
>> Matheus.
>
> Most straightforward that I know of is the following:
>
>    arr = arr[0 .. position] ~ [ newValue ] ~ arr[position + 1 
> .. $];
>
> But if you don't actually want to modify the data, you can 
> merely access the elements in-place by std.range.chain:
>
> import std.stdio;
> import std.range;
>
> void main()
> {
>    int[] arr = [0,1,2,3,4,5,6,7,8,9];
>    immutable position = arr.length / 2;
>    immutable newValue = 42;
>
>    auto r = chain(arr[0 .. position], [ newValue ], 
> arr[position + 1 .. $]);
>    writeln(r);
> }
>
> 'r' above is a lazy range that just provides access to the 
> three ranges given to it. 'arr' does not change in any way.
>
> Ali

Hi Ali,

You gave me a tip with this "chain" feature.

I changed a few lines of your code, and it worked as I wanted:


import std.stdio;
import std.range;
import std.array;

void main()
{
     int[] arr = [0,1,2,3,4,5,6,7,8,9];
     immutable position = arr.length / 2;
     immutable newValue = 42;

     auto r = chain(arr[0 .. position], [ newValue ], arr[position 
.. $-1]);
     arr = array(r);

     foreach(int i; arr)
         writefln("%d", i);
}


Thanks,

Matheus.