How to use $ in UDTs...

[Don Clugston]

Don Clugston wrote:
> Don Clugston wrote:
>> Oskar Linde wrote:
>>> Bill Baxter wrote:
>>>
>>>> Anyway, f[i][j][k] syntax is much more difficult to read than 
>>>> f[i,j,k].  So I think the latter is what we should be shooting for.
>>>
>>> I agree, and for what it is worth it is possible to implement 
>>> multidimensional indexing and slicing for UDTs today. The only thing 
>>> lacking is the ability to use the .. and $ tokens. For example:
>>>
>>> f[i, all, all, j, all, end-1, all, range(1, end)]
>>>
>>> gets translated into quite optimal code. The only variables that get 
>>> passed to the indexing function is (i,j,1,1) and no temporaries need 
>>> to be created. I guess that with some additional compiler supported 
>>> sugaring, the above could become something like:
>>>
>>> f[i, .. , .. , j, .. , $-1, .. , 1..$]
>>
>> Try putting this line at the top of your file.
>>
>> enum : int { __dollar = int.max }
>>
>> Of course you have to add (length-int.max) to any indices you get, for 
>> any index > (int.max-length).
>>
>> Gotta love these easter eggs....
> 
> BTW this means you can use arrays as an approximation to a slice, and 
> write:
> 
> f[i, [0,$], [0,$], k, [0,$], $-1, [0,$], [1,$] ].
> 
> And every index element will be int or int[2], depending on whether it's 
> a slice or an index.
> 
> Of course you can define
> const all= [0,int.max];
> if you prefer that.

Final answer: null = full slice.

struct F
{
  opIndex(T...)(T indices) { ... }
}

F f;
f[i, null, null, k, null, $-1, null, [1,$] ].

Much better than what I was asking for.