How to use $ in UDTs...

[Don Clugston]

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.