How to use $ in UDTs...
Don Clugston
dac at nospam.com.au
Thu Nov 22 05:52:43 PST 2007
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.
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