http://d.puremagic.com/issues/show_bug.cgi?id=3938
Summary: semantics of casting arrays need to be reworked
Product: D
Version: 2.000
Platform: All
URL: http://www.digitalmars.com/d/arrays.html
OS/Version: All
Status: NEW
Keywords: rejects-valid, spec
Severity: major
Priority: P2
Component: www.digitalmars.com
AssignedTo: nob...@puremagic.com
ReportedBy: mrmoc...@gmx.de
Blocks: 2494
--- Comment #0 from Trass3r <mrmoc...@gmx.de> 2010-03-12 13:09:28 PST ---
It needs to be clarified when a reinterpret_cast is done and when the elements
are converted to the new type depending on whether it is an array literal,
another array expression, an array of structs, classes or interfaces AND
whether it is a constant array or not.
A sane and consistent solution is required.
The only information at all is hidden deep inside the huge expressions
documentation:
http://www.digitalmars.com/d/2.0/expression.html#ArrayLiteral
What is the rationale for this inconsistency?
(Also, is this information correct? For example I thought array literals are
dynamic arrays now ("The AssignExpressions form the elements of a static
array")?
Additionally: "The type of the first element is taken to be the type of all the
elements" ->
http://www.digitalmars.com/d/archives/digitalmars/D/casting_array_literals_doesn_t_work_as_stated_in_the_docs_104333.html#N104334)
We already had several discussions about it here:
http://www.digitalmars.com/d/archives/digitalmars/D/learn/converting_a_byte_array_to_a_struct_array_18526.html
followed by
http://www.digitalmars.com/d/archives/digitalmars/D/casting_array_literals_doesn_t_work_as_stated_in_the_docs_104333.html
For example, I want a byte array to be saved in the executable file which is
reinterpreted in the code as RGB structs:
RGB[256] PALETTE = cast(RGB[256]) [
0x00, 0x00, 0x00, 0xE3, 0x53, 0x00,
0xCF, 0x4B, 0x07, 0xBF, 0x43, 0x0F, ...
doesn't work cause of "non-constant expression"
RGB[256] PALETTE = (cast(RGB[]) [
0x00, 0x00, 0x00, 0xE3, 0x53, 0x00,
0xCF, 0x4B, 0x07, 0xBF, 0x43, 0x0F, ...
]) (0 .. 256);
compiles, but yields empty structs (cause it tries to cast each element to a
struct instance if I'm not mistaken)
RGB[] PALETTE = (cast(RGB*) cast(ubyte[]) [...])[0..256];
makes it work, but of course it's a bit hacky.
Also see:
http://codepad.org/OGjXADdu
and my answer:
http://codepad.org/bvk63OPw
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