Slices, appending to arbitrary position

[Chris Cain]

On Monday, 30 December 2013 at 18:19:54 UTC, Dfr wrote:
> This simple example:
>
> string[] a;
> a[10] = "hello";
>
> Gives me: core.exception.RangeError: Range violation
>
> I know about this way:
>
> string[] a;
> a = new string[11];
> a[10] = "hello";
>
> But what if i need do this many times with the same array like 
> this:
>
> a[10] = "a";
> ...
> a[1] = "b";
> ..
> a[1000] = "c";

Does it *need* to be an array for some reason?
If so, resize the array prior.

Something like:

     // index is the position you're changing
     // value is the value you're changing to
     if(a.length <= index) {
         a.length = index+1;
     }
     a[index] = value;

If you're just mapping integers to strings, then you're probably 
looking for an associative array:
http://dlang.org/hash-map.html

This is probably more like what you actually want:

     string[size_t] a;
     a[1] = "works fine";
     a[10] = "also works fine";



> isn't this will be inefficient ?

Yes. Resizing the array many times is very inefficient. Either 
use an associative array or know ahead of time what your array's 
length needs to be (or, at least, what it will "likely" need to 
be).