auto x = new int[][](n,m);

But one cannot freely assign anywhere in x:

x[3,6] = 4 crashes.

I, can, of course, convert everything to a linear matrix and index by i+w*j, but what's the point of having multidimensional matrices in D if they don't allocate them fully?

On 22/01/2017 9:05 PM, Jot wrote:
> auto x = new int[][](n,m);
>
> But one cannot freely assign anywhere in x:
>
> x[3,6] = 4 crashes.
>
> I, can, of course, convert everything to a linear matrix and index by
> i+w*j, but what's the point of having multidimensional matrices in D if
> they don't allocate them fully?

It does allocate them fully, you're indexing them wrong.

void main() {
	auto x = new int[][](1, 2);
	x[0][1] = 3;	
}

On Sunday, 22 January 2017 at 08:07:26 UTC, rikki cattermole wrote:
> On 22/01/2017 9:05 PM, Jot wrote:
>> auto x = new int[][](n,m);
>>
>> But one cannot freely assign anywhere in x:
>>
>> x[3,6] = 4 crashes.
>>
>> I, can, of course, convert everything to a linear matrix and index by
>> i+w*j, but what's the point of having multidimensional matrices in D if
>> they don't allocate them fully?
>
> It does allocate them fully, you're indexing them wrong.
>
> void main() {
> 	auto x = new int[][](1, 2);
> 	x[0][1] = 3;	
> }

No, that isn't the reason, it was cause I was going past the end when I added some new code(the [3,6] was suppose to be [3][6]).

I tried it before and it was crashing before I added the new code and visualD seems to not be updating variable values properly anymore so I can't really debug ;/


In anycase, what is the correct notation for indexing?

x = new int[][](width, height)

and x[height][width] or x[width][height]?

> In anycase, what is the correct notation for indexing?
>
> x = new int[][](width, height)
>
> and x[height][width] or x[width][height]?

It's x[width][height], but because indexing is 0-based, largest valid indexes are
x[width-1][height-1].

On Sunday, 22 January 2017 at 08:18:35 UTC, Jot wrote:
> On Sunday, 22 January 2017 at 08:07:26 UTC, rikki cattermole wrote:
>> On 22/01/2017 9:05 PM, Jot wrote:
>>> auto x = new int[][](n,m);
>>>
>>> But one cannot freely assign anywhere in x:
>>>
>>> x[3,6] = 4 crashes.
>>>
>>> I, can, of course, convert everything to a linear matrix and index by
>>> i+w*j, but what's the point of having multidimensional matrices in D if
>>> they don't allocate them fully?
>>

If you want multidimensional array (matrices, tensors) use either
std.experimental.ndslice or mir.ndslice (they are (effectively) the
same package, one is a dev version of the other).
see https://github.com/libmir/

>> It does allocate them fully, you're indexing them wrong.
>>
>> void main() {
>> 	auto x = new int[][](1, 2);
>> 	x[0][1] = 3;	
>> }
>
> No, that isn't the reason, it was cause I was going past the end when I added some new code(the [3,6] was suppose to be [3][6]).
>
> I tried it before and it was crashing before I added the new code and visualD seems to not be updating variable values properly anymore so I can't really debug ;/
>
>
> In anycase, what is the correct notation for indexing?
>
> x = new int[][](width, height)
>
> and x[height][width] or x[width][height]?

The trick is to remember that in D int[][] is effectively (int[])[].
As such indexing the outer dimension gives you the inner dimension.

so x[height-1][width-1] will give you the "last" element.

visually if - is an int
[ - - - - - - - - -]
[ - - - - 9 - - - -]
[ - - - - - - - - -]
the first index (i.e index it once and it) gives you the row, index it again to get the value.

so that 9 is
x[1][4]