http://d.puremagic.com/issues/show_bug.cgi?id=6345

           Summary: A different kind of vector operation
           Product: D
           Version: unspecified
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: bearophile_hugs@eml.cc


--- Comment #0 from bearophile_hugs@eml.cc 2011-07-18 12:15:46 PDT ---
Currently (DMD 2.054) this is not allowed, but a vector op like this is
sometimes useful to me:

struct Foo {
    int x, y;
    int[100] array;
}
void main() {
    auto foos = new Foo[100];
    foos[].y += 10; // ********
}


For the programmer I think the meaning of such code is easy enough to understand and use.

At the moment I don't see the need to define a operator overload for this too (I mean something like opSliceUnary).


Don notes:

> An interesting use case:
> void main()
> {
>     cdouble[100] foos;
>     foos[].re = 5.0;
> }



Wilfried Kirschenmann suggests:

> void main() {
>   auto foos = new Foo[100];
>   auto ints = new int[100]
>   ints = foos[].y;
> }
> 
> This would simplify the wrinting of numerous application, especially in the writing of image/video processing (eg. rgb2yuv conversions) This would also simplify the writing of template library transforming "array of struct" to "struct of arrays" in a transparent manner for the library user.


Andrej Mitrovic notes (I don't understand this):

> float[] buffers = malloc..;
> float*[] CBuffers = buffers[].ptr;

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kennytm@gmail.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |kennytm@gmail.com


--- Comment #1 from kennytm@gmail.com 2011-07-18 12:44:34 PDT ---
What if I define


ref int y(Foo[] f) {
    return f[0].x;
}


?

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--- Comment #2 from bearophile_hugs@eml.cc 2011-07-27 13:56:06 PDT ---
Another possible purpose. Given this matrix:

auto M = new double[][](10, 20);

This:

M[][1] = 1.0;

Means:

foreach (row; p)
    row[1] = 1.0;


This replaces some usages of std.range.transversal().

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Don <clugdbug@yahoo.com.au> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |clugdbug@yahoo.com.au


--- Comment #3 from Don <clugdbug@yahoo.com.au> 2011-07-28 00:36:12 PDT ---
All these operations require the use of strided slices, which would be a huge amount of work to implement. Also, there are a plethora of corner cases.

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--- Comment #4 from bearophile_hugs@eml.cc 2011-07-28 05:15:59 PDT ---
(In reply to comment #3)
> All these operations require the use of strided slices, which would be a huge amount of work to implement. Also, there are a plethora of corner cases.

I see. Those corner cases are bad. If you think this is too much work for the gain I'll close this enhancement request, to leave similar functionalities to matrix libraries.

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