• Trass3r <mrmocool gmx.de> Dec 29 2009
• Trass3r <mrmocool gmx.de> Dec 29 2009
• "Steven Schveighoffer" <schveiguy yahoo.com> Dec 29 2009
• Trass3r <mrmocool gmx.de> Dec 29 2009
• Trass3r <mrmocool gmx.de> Dec 30 2009
• "Steven Schveighoffer" <schveiguy yahoo.com> Dec 29 2009
• "Steven Schveighoffer" <schveiguy yahoo.com> Dec 29 2009
• grauzone <none example.net> Dec 29 2009
• Trass3r <mrmocool gmx.de> Dec 30 2009
• Trass3r <mrmocool gmx.de> Jan 02 2010
• grauzone <none example.net> Jan 02 2010

Trass3r <mrmocool gmx.de> writes:

I got some RGB palette in a byte array which I'd like to convert or 
"map" to an RGB struct array, isn't this easily possible without using 
dozens of struct constructors?


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 (and doesn't seem right anyway).

Trass3r <mrmocool gmx.de> writes:

Just remembered the old casting hack:

RGB[] PALETTE = (cast(RGB*) cast(ubyte[]) [...])[0..256];

It works but is there perhaps another nicer possibility?

"Steven Schveighoffer" <schveiguy yahoo.com> writes:

On Tue, 29 Dec 2009 07:56:04 -0500, Trass3r <mrmocool gmx.de> wrote:

 I got some RGB palette in a byte array which I'd like to convert or  
 "map" to an RGB struct array, isn't this easily possible without using  
 dozens of struct constructors?


 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 (and doesn't seem right anyway).


What is RGB's structure?

I would expect something like this to work:

RGB[256] PALETTE = [
{0x00, 0x00, 0x00},
{0xE3, 0x53, 0x00},
...
];

Assuming RGB is a struct of 3 ubyte members...

-Steve

Trass3r <mrmocool gmx.de> writes:

Steven Schveighoffer schrieb:
 What is RGB's structure?
 
 I would expect something like this to work:
 
 RGB[256] PALETTE = [
 {0x00, 0x00, 0x00},
 {0xE3, 0x53, 0x00},
 ...
 ];
 
 Assuming RGB is a struct of 3 ubyte members...
 


Yeah, simply 3 ubytes.
But IIRC I read that struct literals will be removed in D2 so I didn't 
test that approach.

Trass3r <mrmocool gmx.de> writes:

Steven Schveighoffer schrieb:
 You are right, I asked the question on that thread of whether it was 
 worth keeping struct literals for this purpose.


 And the answer (created by bearophile): http://codepad.org/8HnF62s2
 


Yeah, I know but if you got that data out of some file like the resource 
section of a game exe in my case, adding the struct constructors is 
cumbersome.

"Steven Schveighoffer" <schveiguy yahoo.com> writes:

On Tue, 29 Dec 2009 10:03:50 -0500, Trass3r <mrmocool gmx.de> wrote:

 Steven Schveighoffer schrieb:
 What is RGB's structure?
  I would expect something like this to work:
  RGB[256] PALETTE = [
 {0x00, 0x00, 0x00},
 {0xE3, 0x53, 0x00},
 ...
 ];
  Assuming RGB is a struct of 3 ubyte members...


 Yeah, simply 3 ubytes.
 But IIRC I read that struct literals will be removed in D2 so I didn't  
 test that approach.


You are right, I asked the question on that thread of whether it was worth  
keeping struct literals for this purpose.

-Steve

"Steven Schveighoffer" <schveiguy yahoo.com> writes:

On Tue, 29 Dec 2009 10:37:43 -0500, Steven Schveighoffer  
<schveiguy yahoo.com> wrote:

 On Tue, 29 Dec 2009 10:03:50 -0500, Trass3r <mrmocool gmx.de> wrote:

 Steven Schveighoffer schrieb:
 What is RGB's structure?
  I would expect something like this to work:
  RGB[256] PALETTE = [
 {0x00, 0x00, 0x00},
 {0xE3, 0x53, 0x00},
 ...
 ];
  Assuming RGB is a struct of 3 ubyte members...


 Yeah, simply 3 ubytes.
 But IIRC I read that struct literals will be removed in D2 so I didn't  
 test that approach.


 You are right, I asked the question on that thread of whether it was  
 worth keeping struct literals for this purpose.


And the answer (created by bearophile): http://codepad.org/8HnF62s2

-Steve

grauzone <none example.net> writes:

Trass3r wrote:
 I got some RGB palette in a byte array which I'd like to convert or 
 "map" to an RGB struct array, isn't this easily possible without using 
 dozens of struct constructors?
 
 
 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 (and doesn't seem right anyway).


You've hit both an anti-feature and a bug.

First the anti-feature: [0xAB, ...] will yield an int[], not a ubyte[] 
(I guess ubyte[] is what you're expecting). If you cast two arrays, the 
compiler will reinterpret cast all data. The result won't be what you 
intended.

Second, the bug: casting arrays at compiletime seems to behave 
differently from casting at runtime. Casting at compiletime doesn't 
reinterpret cast, it does conversion! Demonstration here: 
http://codepad.org/OGjXADdu

Feel free to file some bug reports.

Trass3r <mrmocool gmx.de> writes:

grauzone schrieb:
 First the anti-feature: [0xAB, ...] will yield an int[], not a ubyte[] 
 (I guess ubyte[] is what you're expecting). If you cast two arrays, the 
 compiler will reinterpret cast all data. The result won't be what you 
 intended.
 


cast(ubyte[]) it (where conversion is expected) for my reinterpret casting:

RGB[] PALETTE = (cast(RGB*) cast(ubyte[]) [...])[0..256];


 Second, the bug: casting arrays at compiletime seems to behave 
 differently from casting at runtime. Casting at compiletime doesn't 
 reinterpret cast, it does conversion! Demonstration here: 
 http://codepad.org/OGjXADdu
 


You're right. But it only concerns casting to a struct(?) or an array of 
structs, right?!. Conversion is correct for standard arrays, but struct 
arrays need to be reinterpret cast (correct me if I'm wrong, I can't 
imagine how conversion could be reasonably used. Only thing might be 
casting an array of structs to another array of structs but I don't know 
any valid use-case).

Trass3r <mrmocool gmx.de> writes:

grauzone schrieb:
 Second, the bug: casting arrays at compiletime seems to behave 
 differently from casting at runtime. Casting at compiletime doesn't 
 reinterpret cast, it does conversion! Demonstration here: 
 http://codepad.org/OGjXADdu
 
 Feel free to file some bug reports.


Just found out this is stated as a feature in the docs.
http://www.digitalmars.com/d/2.0/expression.html#ArrayLiteral

http://codepad.org/bvk63OPw

grauzone <none example.net> writes:

Trass3r wrote:
 grauzone schrieb:
 Second, the bug: casting arrays at compiletime seems to behave 
 differently from casting at runtime. Casting at compiletime doesn't 
 reinterpret cast, it does conversion! Demonstration here: 
 http://codepad.org/OGjXADdu

 Feel free to file some bug reports.


 Just found out this is stated as a feature in the docs.
 http://www.digitalmars.com/d/2.0/expression.html#ArrayLiteral


Interesting. then this is an anti-feature too. At least it sounds like a 
very bad idea. The compiler/language tries to be "smart" here, but only 
introduces inconsistencies.

 http://codepad.org/bvk63OPw