Using std.algorithm how to uniq and sort a multidimensional array?

[bearophile]

Gary Willoughby:

>     string[][] tags;
>
>     tags = tags.uniq!("a[0][1] == b[1][1]").array;

I think the right abstraction for your use case is:

auto tags = tags.flatten.uniq.array;

Where a std.range.flatten should take a range, range of ranges, 
range of range of ranges, etc, and yield the items scanning them 
by rows (flatten takes a template argument enumeration to change 
the scanning pattern: by rows, by columns, bidirectional rows, 
zig-zag, Hamming curve, Z curve, 2D rectangular blocks).

Probably flatten should have a compile-time argument to tell it 
what a iterable range means. And an optional run-time argument 
"maxDepth".

Ideally flatten should yield references of the items, so you can 
increase all matrix items by 1 with code like:

int[][][] matrix = ...;
foreach (ref item; mat.flatten)
     item++;

Bye,
bearophile