Hi,

How do I initialise a dynamic array of dynamic arrays?

struct MyData {
  SysTime stamp;
  short[] data;

  this(size_t size) {
    data = new short[size];
  }
}

MyDataArray mda;

how to initialise mda?

mda = new MyDataArray ?

Thanks.

Regards, -=mike=-

On Tue, 30 Sep 2014 15:57:57 +0000
Mike James via Digitalmars-d-learn <digitalmars-d-learn@puremagic.com>
wrote:

> How do I initialise a dynamic array of dynamic arrays?
do you mean something like this: `int[][] a`? if yes, do this:

  auto a = new int[][](42, 69);

and you'll get `int[42][69] a`.

heh, people again confused by `new Type[amount]` syntax. that is concrete sign that this syntax will live forever.

On Tuesday, 30 September 2014 at 16:07:28 UTC, ketmar via Digitalmars-d-learn wrote:
> On Tue, 30 Sep 2014 15:57:57 +0000
> Mike James via Digitalmars-d-learn <digitalmars-d-learn@puremagic.com>
> wrote:
>
>> How do I initialise a dynamic array of dynamic arrays?
> do you mean something like this: `int[][] a`? if yes, do this:
>
>   auto a = new int[][](42, 69);
>
> and you'll get `int[42][69] a`.
>
> heh, people again confused by `new Type[amount]` syntax. that is
> concrete sign that this syntax will live forever.

Thanks ketmar,

You'll notice that it's actually a dynamic array of structs containing dynamic arrays - does this change your initializing?

Regards, -=mike=-

On 9/30/14 12:40 PM, Mike James wrote:
> On Tuesday, 30 September 2014 at 16:07:28 UTC, ketmar via
> Digitalmars-d-learn wrote:

>>   auto a = new int[][](42, 69);

...

>
> You'll notice that it's actually a dynamic array of structs containing
> dynamic arrays - does this change your initializing?

That is what his code does.

-Steve

On Tuesday, 30 September 2014 at 17:22:32 UTC, Steven Schveighoffer wrote:
> On 9/30/14 12:40 PM, Mike James wrote:
>> On Tuesday, 30 September 2014 at 16:07:28 UTC, ketmar via
>> Digitalmars-d-learn wrote:
>
>>>  auto a = new int[][](42, 69);
>
> ...
>
>>
>> You'll notice that it's actually a dynamic array of structs containing
>> dynamic arrays - does this change your initializing?
>
> That is what his code does.
>
> -Steve

Hi Steve,

It's true that his code initialises an array of arrays - but my array is an array of structs containing a dynamic array.

Regards, -=mike=-

On Tuesday, 30 September 2014 at 15:57:58 UTC, Mike James wrote:
> Hi,
>
> How do I initialise a dynamic array of dynamic arrays?
>
> struct MyData {
>   SysTime stamp;
>   short[] data;
>
>   this(size_t size) {
>     data = new short[size];
>   }
> }
>
> MyDataArray mda;
>
> how to initialise mda?
>
> mda = new MyDataArray ?
>
> Thanks.
>
> Regards, -=mike=-

I think I've found a way...

struct MyData {
  SysTime stamp;
  short[] data;

  this(size_t size) {
    data = new short[size];
  }
}

MyDataArray[] mda; <--- sorry, missing the []s in the original question...

so in the constructor...

this(size_t x, size_t y) {
  mda = new MyDataArray[](x);
        foreach(n, _; mda) mda[n].data.length = y;
}

Is there a simpler way?

Regards, -=mike=-

On Wed, 01 Oct 2014 07:45:48 +0000
Mike James via Digitalmars-d-learn <digitalmars-d-learn@puremagic.com>
wrote:

> so in the constructor...
> 
> this(size_t x, size_t y) {
>    mda = new MyDataArray[](x);
>          foreach(n, _; mda) mda[n].data.length = y;
> }
> 
> Is there a simpler way?
sorry, but no. btw, if MyDataArray is struct, you should do this:

  foreach (ref m; mda) m.data.length = y;

or even this:

  foreach (ref m; mda = new MyDataArray[](x)) m.data.length = x;


the thing is that without 'ref' you operates on the local copy, not on the real array element.

On Wednesday, 1 October 2014 at 08:08:06 UTC, ketmar via Digitalmars-d-learn wrote:
> On Wed, 01 Oct 2014 07:45:48 +0000
> Mike James via Digitalmars-d-learn <digitalmars-d-learn@puremagic.com>
> wrote:
>
>> so in the constructor...
>> 
>> this(size_t x, size_t y) {
>>    mda = new MyDataArray[](x);
>>          foreach(n, _; mda) mda[n].data.length = y;
>> }
>> 
>> Is there a simpler way?
> sorry, but no. btw, if MyDataArray is struct, you should do this:
>
>   foreach (ref m; mda) m.data.length = y;
>
> or even this:
>
>   foreach (ref m; mda = new MyDataArray[](x)) m.data.length = x;
>
>
> the thing is that without 'ref' you operates on the local copy, not on
> the real array element.

Thanks ketmar, that did the trick.

Regards, -=mike=-

On 10/1/14 3:13 AM, Mike James wrote:
> Hi Steve,
>
> It's true that his code initialises an array of arrays - but my array is
> an array of structs containing a dynamic array.
>
> Regards, -=mike=-

Ah, ok.

There is no trivial way to do it. Unlike C++, struct default ctors cannot be overridden.

I see your question has been answered, but I would just tweak it a bit:

foreach(ref m; mda) m.data = new short[y];

Only reason for that is, setting length will call some specialized function which eventually ends up doing exactly the same thing. The above is clearer and more correct IMO.

-Steve