Simple casting?

[Alex]

On Tuesday, 26 November 2019 at 05:17:54 UTC, Taylor R Hillegeist 
wrote:
> On Tuesday, 26 November 2019 at 05:05:48 UTC, Taylor R 
> Hillegeist wrote:
>> I'm attempting to do a segment group.
>>
>> details:
>> alias ProbePoint[3]=triple;
>> triple[] irqSortedSet = UniqueTriples.keys
>> 				.sort!("a[1].irqid < b[1].irqid",SwapStrategy.stable)
>> 				.array;		
>> 83:triple[][] irqSortedSets = irqSortedSet.chunkBy!((a,b) => 
>> a[1].irqid == b[1].irqid);	
>>
>>
>> GetAllTriplesExtractFileIrqSplit.d(83): Error: cannot 
>> implicitly convert expression `chunkBy(irqSortedSet)` of type 
>> `ChunkByImpl!(__lambda4, ProbePoint[3][])` to 
>> `ProbePoint[3][][]`
>>
>> I have something that looks like a triple[][] but I can't seem 
>> to get that type out.
>> when I add .array it converts to a Group which doesn't make 
>> sense to me because I'm not using a unary comparison. Any 
>> thought?
>
> a simpler example:
>
> import std.algorithm.comparison : equal;
> import std.array;
> // Grouping by particular attribute of each element:
> uint[3][] data = [
>     [1, 1,0],
>     [1, 2,0],
>     [2, 2,0],
>     [2, 3,0]
> ];
>
> uint[3][][] r1 = data.chunkBy!((a,b) => a[0] == b[0]);
>
> fails in the same way.

What exactly is the problem, as this works for me if I understood 
your goal correctly:

´´´
void main()
{
     import std.algorithm.comparison : equal;
     import std.array;
     import std;
     // Grouping by particular attribute of each element:
     uint[3][] data = [
         [1, 1,0],
         [1, 2,0],
         [2, 2,0],
         [2, 3,0]
     ];

     auto r1 = data.chunkBy!((a,b) => a[0] == b[0]);
}
´´´

If it is the type of the return value --> the return value of 
chunkBy has a different one compared to the input. Instead, you 
get an abstracted range whereas the input data serves as a source.