Hello,

I was looking over http://dlang.org/spec/arrays.html#rectangular-arrays:

And I've found that D multidimensional arrays are Rectangular, so it's impossible to create non-rectangular multidimensional static array like:

int[2][5] arr;

?

On Tuesday, 19 January 2016 at 02:47:04 UTC, albert wrote:
> Hello,
>
> I was looking over http://dlang.org/spec/arrays.html#rectangular-arrays:
>
> And I've found that D multidimensional arrays are Rectangular, so it's impossible to create non-rectangular multidimensional static array like:
>
> int[2][5] arr;
>
> ?

How is that not rectangular? It's sounds like you're confusing it with "square".

On Tuesday, 19 January 2016 at 02:54:03 UTC, cym13 wrote:
>> int[2][5] arr;
>>
>> ?
>
> How is that not rectangular? It's sounds like you're confusing it with "square".

Ow my problem is:

int[2][2] arr;  // This works

int[2][5] arr;  // This not working

And I'd like to create the former.

Well maybe it was my fault, but anyway, here's a small example of what I was working on:

void main(){
	// Array 1	
	int[2][2] arr1;

	arr1[0][0] = 1;
	arr1[0][1] = 2;
	arr1[1][0] = 3;
	arr1[1][1] = 4;

	// Array 2
	int[1][2] arr2;
	
	//arr2[0][0] = 1;
	//arr2[0][1] = 2; // <- Error
	
	arr2[0][0] = 1;
	arr2[1][0] = 2;
}

So for what I can see on Array 2 is the column/row works otherwise.

It's strange since I was declaring int[1][2] (1 row / 2 columns) and then accessing as:

	arr2[0][0] = 1;
	arr2[1][0] = 2;

Seems like 2 rows and 1 column. This makes sense?

On Tuesday, 19 January 2016 at 03:20:30 UTC, albert00 wrote:
> [...]

You're not really creating a rectangular array - what you're making is an array *of arrays*:

int[10][5] a; // An array of 5 (int[10])

writeln(typeof(a).stringof);      // int[10][5]
writeln(typeof(a[4]).stringof);    // int[10]
writeln(typeof(a[4][9]).stringof); // int

The recently accepted `std.experimental.ndslice` module provides a real multi-dimensional array interface:
    http://dlang.org/phobos-prerelease/std_experimental_ndslice.html

(There might be something else relevant in Phobos as well, with a less numerically-oriented focus; I'm not sure.)

On 01/18/2016 07:20 PM, albert00 wrote:

> It's strange since I was declaring int[1][2] (1 row / 2 columns) and
> then accessing as:
>
>      arr2[0][0] = 1;
>      arr2[1][0] = 2;
>
> Seems like 2 rows and 1 column. This makes sense?

Yes, it makes sense and its consistent. This is one of many little things that D is an improvement over C and C++.

Static array type syntax is always the following:

    Type[length]

For example, the following is a row with two columns:

    int[2]

When you want a certain number of those, you follow the same array definition syntax:

    Type[length]

Since each element is int[2] in this case, for 3 rows we get:

    int[2][3]

So, in order to get 1 row of 2 columns, you would write

    int[2][1]

Accessing elements is consistent as well:

    var[index]

So,

    arr2[0]

would be the first row, which has two columns; which is further accessed by another index:

    arr2[0][1]

is first row, second column.

Ali

On Tuesday, 19 January 2016 at 05:32:07 UTC, Ali Çehreli wrote:

Ali, look what you said:

> For example, the following is a row with two columns:
>
>     int[2]

Then you said:

> So, in order to get 1 row of 2 columns, you would write
>
>     int[2][1]

So the first pair of square-brackets is the column and second is the row as you said above, but look what happens when I try to access thinking that way:

void main(){
	int[2][1] arr; // 2 columns & 1 row as Ali said...
	
	arr[0][0] = 1;
	arr[1][0] = 2;
}

ERROR:

/d609/f167.d(14): Error: array index 1 is out of bounds arr[0 .. 1]
/d609/f167.d(14): Error: array index 1 is out of bounds arr[0 .. 1]


So now the first pair of brackets in fact is the ROW and the second is the COLUMN, because this works:

void main(){
	int[2][1] arr; // 2 columns & 1 row
	
	arr[0][0] = 1;
	arr[0][1] = 2;
}

Maybe I'm really dumb, but you need to agree that even with your good explanation it still doesn't making sense.

Albert.

On 01/18/2016 11:12 PM, Albert00 wrote:
> On Tuesday, 19 January 2016 at 05:32:07 UTC, Ali Çehreli wrote:
>
> Ali, look what you said:
>
>> For example, the following is a row with two columns:
>>
>>     int[2]
>
> Then you said:
>
>> So, in order to get 1 row of 2 columns, you would write
>>
>>     int[2][1]

To rephrase myself, that is an array of 1 element, where the element type is int[2]. So the only valid index is 0, which gives you an element of int[2]. (You can further index into that element of course.)

> So the first pair of square-brackets is the column and second is the row
> as you said above,

I stress the fact that it is always the following syntax:

    Type[length]

So, again, if we have an array of 1-element where the elements are of type int[2], then it is this (space added for readability):

    int[2] [1]

> but look what happens when I try to access thinking
> that way:

I suspect C and C++ way for inside-out (or is it outside-in) syntax is affecting your thinking. ;)

> void main(){
>      int[2][1] arr; // 2 columns & 1 row as Ali said...
>
>      arr[0]

That one gives you the first element.

> [0] = 1;

and that one gives you the first element of that first element.

>      arr[1][0] = 2;

Sorry, there is no element-1 for the arr: That has only one element.

> }
>
> ERROR:
>
> /d609/f167.d(14): Error: array index 1 is out of bounds arr[0 .. 1]
> /d609/f167.d(14): Error: array index 1 is out of bounds arr[0 .. 1]
>
>
> So now the first pair of brackets in fact is the ROW and the second is
> the COLUMN, because this works:
>
> void main(){
>      int[2][1] arr; // 2 columns & 1 row

Yes, that's exactly what I said. :)

>      arr[0][0] = 1;
>      arr[0][1] = 2;
> }
>
> Maybe I'm really dumb,

Not at all. I blame C and C++. ;)

> but you need to agree that even with your good explanation it
> still doesn't making sense.

I don't agree: It makes sense and is consistent. :)

> Albert.

Ali

On Tuesday, 19 January 2016 at 04:50:18 UTC, tsbockman wrote:
> On Tuesday, 19 January 2016 at 03:20:30 UTC, albert00 wrote:
>> [...]
>
> ... what you're making is an array *of arrays*:

Maybe I was misunderstood, because in fact that is what I was making an array of arrays, but my problem in fact was in accessing it.

Like I said above:

I was declaring int[1][2] arr:

But to access I need to invert the columns like:

	arr2[0][0] = 1;
	arr2[1][0] = 2;


> int[10][5] a; // An array of 5 (int[10])

Using your example, in my head I'd access the last element as:

a[9][4] but that would give me an error:

Error: array index 9 is out of bounds arr[0 .. 5]

So I need to invert a[4][9].

Again seems a bit strange "FOR ME" since I declare in one way and access the other way.

albert.

PS: I'm changing my name because I think there is another user with the same name, that Icon is not mine.

On Tuesday, 19 January 2016 at 07:19:54 UTC, Ali Çehreli wrote:
> ...

Well anyway thanks for your help. For now I'll just think the otherwise. :)

Albert.