Hi!
Explain me please,what's wrong with this code:

struct NDimensionalArray(T,alias size)
	if(is(typeof(size) _ == int[n],int n) &&
	   n > 0)
{
	static if(n > 1)
		NDimensionalArray!(T,n - 1,size[1..$]) m_array[size[0]];
	else
		T m_array[size[0]];
	alias m_array this;
}

void main()
{
	NDimensionalArray!(int,[2,2]) array;
	array[0][1] = 1;
}

It fails with message:
Error: template instance NDimensionalArray!(int, [2, 2]) NDimensionalArray!(int, [2, 2]) does not match template declaration NDimensionalArray(T, alias size) if (is(typeof(size) _ == int[n],int n) && n > 0)
on dmd git-head.

This is an answer to just your title question.

A lot of time ago typeof([2,2]) was int[2]. This was efficient, but in most cases this was a source of troubles and bugs. So now a [2,2] is a heap-allocated dynamic array of type int[]. Some persons have askes for a fixed-sized array litera, like s[2,2] but nothing has happened on this so far.

Bye,
bearophile

On Friday, 8 March 2013 at 22:59:40 UTC, bearophile wrote:
> This is an answer to just your title question.
>
> A lot of time ago typeof([2,2]) was int[2]. This was efficient, but in most cases this was a source of troubles and bugs. So now a [2,2] is a heap-allocated dynamic array of type int[]. Some persons have askes for a fixed-sized array litera, like s[2,2] but nothing has happened on this so far.
>
> Bye,
> bearophile

Thank you very much.

On Friday, 8 March 2013 at 23:03:47 UTC, Zhenya wrote:
> On Friday, 8 March 2013 at 22:59:40 UTC, bearophile wrote:
>> This is an answer to just your title question.
>>
>> A lot of time ago typeof([2,2]) was int[2]. This was efficient, but in most cases this was a source of troubles and bugs. So now a [2,2] is a heap-allocated dynamic array of type int[]. Some persons have askes for a fixed-sized array litera, like s[2,2] but nothing has happened on this so far.
>>
>> Bye,
>> bearophile
>
> Thank you very much.

Although it's a bit strange,since we can always pass heap allocated array by
using new.

On Friday, 8 March 2013 at 23:03:47 UTC, Zhenya wrote:

Your constraint could be:

if(is(typeof(size) _ == int[]) && size.length > 0)

Also it looks like you are passing 1 too many template args?

static if(n > 1)
  NDimensionalArray!(T,n - 1,size[1..$]) m_array[size[0]];
                             ^^

On Friday, 8 March 2013 at 23:09:07 UTC, cal wrote:
> On Friday, 8 March 2013 at 23:03:47 UTC, Zhenya wrote:
>
> Your constraint could be:
>
> if(is(typeof(size) _ == int[]) && size.length > 0)
>
> Also it looks like you are passing 1 too many template args?
>
> static if(n > 1)
>   NDimensionalArray!(T,n - 1,size[1..$]) m_array[size[0]];
>                              ^^

Yes,it's a typo.But it seems to be ugly pass dynamically allocated array through
a template parameter,because it's size should be compile-time constant.

On Friday, 8 March 2013 at 23:15:30 UTC, Zhenya wrote:
> Yes,it's a typo.But it seems to be ugly pass dynamically allocated array through
> a template parameter,because it's size should be compile-time constant.

Its size is a compile-time constant because it is an array literal. The size is known inside the constraint.

On Friday, 8 March 2013 at 23:18:52 UTC, cal wrote:
> On Friday, 8 March 2013 at 23:15:30 UTC, Zhenya wrote:
>> Yes,it's a typo.But it seems to be ugly pass dynamically allocated array through
>> a template parameter,because it's size should be compile-time constant.
>
> Its size is a compile-time constant because it is an array literal. The size is known inside the constraint.
Yes,really.
I thought that dynamic allocation is runtime operation