[Issue 12062] New: std.range.flatten

[d-bugmail at puremagic.com]

https://d.puremagic.com/issues/show_bug.cgi?id=12062

           Summary: std.range.flatten
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: Phobos
        AssignedTo: nobody at puremagic.com
        ReportedBy: bearophile_hugs at eml.cc


--- Comment #0 from bearophile_hugs at eml.cc 2014-02-02 08:53:12 PST ---
I suggest to add to std.range a range designed to flatten a given n-dimensional
range.

A simple usage example:


int[][] mat = [[1, 2], [3, 4]];
auto mu = mat.flatten.uniq;


std.range.flatten should take a range, range of ranges, range of range of
ranges, etc, and yield the scanned items.

A possible signature:

Flatten flatten(ScanType scan = ScanType.rows(), Range, Targs...)(Range input,
int maxDepth=-1, Targs args);


Where maxDepth tells it a what depth to stop, defaulting to -1 that means to
reach the bottom.


ScanType can be:


enum ScanType {
    rows,
    columns,
    bidirectionalRows,
    bidirectionalColumns,
}


Later more scans can be added:

enum ScanType {
    rows,
    columns,
    bidirectionalRows,
    bidirectionalColumns,
    zigZag,
    hammingCurve,
    zCurve,
    rectBlocked
}


args is used by ScanArgs.rectBlocked, to specify the nx and ny of a 2D block.
The blocked scan is useful because it's a cache-friendly scan for large 2D
arrays.


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

int[][][] mat = [[[1, 2], [3, 4]], [[5, 6], [7, 8]]];
foreach (ref x; mat.flatten)
    x++;

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