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digitalmars.D.bugs - [Issue 6489] New: Should be able to copy double[] to float[]

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=6489

           Summary: Should be able to copy double[] to float[]
           Product: D
           Version: unspecified
          Platform: Other
        OS/Version: Windows
            Status: NEW
          Keywords: rejects-valid
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: dsimcha yahoo.com


--- Comment #0 from David Simcha <dsimcha yahoo.com> 2011-08-13 06:41:27 PDT ---
void main() {
    float[] f;
    double[] d;
    f[] = d[];
}

test9.d(4): Error: cannot implicitly convert expression (d[]) of type double[]
to const(float[])

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next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=6489


bearophile_hugs eml.cc changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bearophile_hugs eml.cc


--- Comment #1 from bearophile_hugs eml.cc 2011-08-13 07:05:04 PDT ---
Why? And only double->float? int->long too?

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--- Comment #2 from David Simcha <dsimcha yahoo.com> 2011-08-13 11:53:29 PDT ---
(In reply to comment #1)

 Why? And only double->float? int->long too?


Of course int -> long should work, too.  Same with anything where implicit
conversions are allowed.  It's just that double -> float is the first case I
stumbled upon.

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Walter Bright <bugzilla digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bugzilla digitalmars.com
           Platform|Other                       |All
         OS/Version|Windows                     |All
           Severity|normal                      |enhancement


--- Comment #3 from Walter Bright <bugzilla digitalmars.com> 2011-08-15
11:50:21 PDT ---
What is the compelling rationale for this? Is there a use case that shows it?

(Also marked as an enhancement request, as it is not a bug.)

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--- Comment #4 from David Simcha <dsimcha yahoo.com> 2011-08-27 07:34:39 PDT ---
The compelling rationale is consistency.  I can assign the elements of a
float[] to a double[] one-by-one, so why not with array-wise operations?

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--- Comment #5 from bearophile_hugs eml.cc 2011-08-27 16:18:55 PDT ---
Please show one or more use case.

Do you want it to be like a reinterpret cast? Currently this works:

void main() {
    ushort[4] a = [1, 2, 3, 4];
    uint[2] b = cast(uint[2])a;
    assert(b == [131073, 262147]);
}

Mixing reinterpret cast with conversion casts is a bad design.

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