Arrays - Inserting and moving data

[Ali Çehreli]

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