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World: r3wp

[Core] Discuss core issues

Gabriele
18-Dec-2011
[2660]
ENBASE
amacleod
18-Dec-2011
[2661]
enbase! Easy! That's what I'm looking for thanks, guys.
Geomol
18-Dec-2011
[2662]
That wasn't clear, but good you solved your problem.
Geomol
19-Dec-2011
[2663]
The R2 dictionary for DETAB say, the string is modified, but it isn't. 
Also only the first tab before the first non-space character is replaced 
by 4 spaces, the rest with 1:

>> s: "^-abc^-def"
== "^-abc^-def"
>> detab s
== "    abc def"
>> s
== "^-abc^-def"

Has this always been this way?
Doc: http://www.rebol.com/docs/words/wdetab.html
Oldes
19-Dec-2011
[2664x4]
== "^-ab^-def"
>> detab s
== "    ab  def"
The behaviour is correct (it's not just replace/all). The dictionary 
must be bad as it does not modify.
The doc above is not so bad, but it's true, that in R3 it's really 
marked as: (Modifies)
But I'm not sure there is anybody left who can fix it.
Geomol
19-Dec-2011
[2668x2]
Is there a reason for this?

>> shift 1 32
== 1
Ah, probably just because 32 is being // 32, as can be seen with 
this:

>> shift 2 32
== 2
>> shift 2 33
== 1
Endo
19-Dec-2011
[2670x2]
Thats right I think:
>> shift 257 32
== 257
>> shift 257 32000
== 257
Geomol
19-Dec-2011
[2672]
which is same result as:

>> shift 257 32000 // 32
== 257
Endo
19-Dec-2011
[2673x3]
Yes
>> shift 257 32001
== 128
>> shift 257 1
== 128
at first glance a bit confusing, but actually it's ok. >> shift 257 
65 == 128
Geomol
19-Dec-2011
[2676x3]
I see potential application malfunction. It's ok to mod by 32 for 
a rotate function, as it gives same result, but not a shift, I think.
Think what will happen, if the application move from 32-bit to 64-bit.
And the mod by 32 for a rotate is only ok on a 32-bit system, on 
a 64-bit it's mod by 64. And only for integers, not binaries etc.
Endo
19-Dec-2011
[2679x2]
That's right, but only if your "interpreter" supports 64 bit integers.
As for R2, its no problem, but for others it is.
Geomol
19-Dec-2011
[2681x2]
Hm, implementing SHIFT in World gives me second thought. The C operators 
>> and << works as doing internal modulus. So checking for number 
of shift will hit on performance. So it's probably better to just 
go with it and let it be up to the user to eventually check for this.
What's the idea with SHIFTing a binary! ?

>> b: #{80402010}   
== #{80402010}
>> shift b 2
== #{20100804}
>> shift b 2
== #{08040201}	; so far so good
>> shift b 2
== #{02010000}	; but now we're loosing information
>> shift b 2
== #{00000000}


So SHIFT of a binary! just shift each byte and don't carry bits over 
to the next. What is this used for?
Endo
20-Dec-2011
[2683]
Its no sense SHIFTing bytes in binary, we can simply use series functions, 
append #{00}, copy/part etc. Shifting bits in binary could be more 
useful for graphics operations (not so sure)
Geomol
20-Dec-2011
[2684]
My example is doing bit shifting right (decreasing value) by 2 bits 
at a time. The bits falling off each byte isn't carried over to the 
next byte.
Endo
20-Dec-2011
[2685x2]
In your example above it shifts bytes not bits. Even shifting bits 
in binary without carrying bits over to the next bytes doesn't look 
useful.
Oh sorry, your second example. Ok.
Louis
26-Dec-2011
[2687x2]
Does anyone have
a function to sort jpeg files from a digital camea by exif date?
Pekr
26-Dec-2011
[2689]
IIRC, someone did EXIF reader. Have you tried looking into rebol.org?
Louis
26-Dec-2011
[2690]
Pekr, thanks for responding. I'll look there.
Pekr
26-Dec-2011
[2691x6]
There are two scripts from Piotr Gapinski, related to EXIF. IIRC 
Oldes did ImageMagick wrapping,maybe it can do some EXIF stuff too 
...
or you can use command line tool like Exiftool, and wrap the result 
using CALLL in REBOL and parse the output?
>> buff: copy ""
>> call/wait/output "exiftool img_0033.jpg" buff
works like a charm, returning several pages of txt formatted output 
- http://www.sno.phy.queensu.ca/~phil/exiftool/
parse/all buff [thru "Create Date" thru ": " copy EXIF-create-date 
to newline]
your value is in EXIF-create-date ....
Louis
26-Dec-2011
[2697]
Wow! Thanks for the help Pekr!
Pekr
26-Dec-2011
[2698]
Dunno how fast it is going to be though, exiftool looks slow, when 
called from REBOL. Might take some time to extract info from xy files 
in directory ...
Oldes
26-Dec-2011
[2699x2]
I have uploaded my latest EXIF-parser version at github - https://github.com/Oldes/rs/blob/master/projects/exif-parser/latest/exif-parser.r

To sort files you can use for example:

dir: %/e/DCIM/100CANON/
t: now/time/precise
result: copy []
foreach file read dir [
	error? try [
		ctx-exif/parse-file dir/:file
		exifdate: ctx-exif/get-tag-value 306
		repend result [exifdate dir/:file]
	]
]

sort/skip result 2

print ["sorted" (length? result) / 2 "files in" now/time/precise 
- t]
result

;>>sorted 120 files in 0:00:00.153
(it could be probably optimized as the script is from year 2004, 
but I don't care too much)
Louis
26-Dec-2011
[2701]
Oldes, many thanks!  I can''t work on this right now, but as soon 
as I can I'll report back.
nve
28-Dec-2011
[2702]
Any news about a new year version of REBOL ?
Pekr
28-Dec-2011
[2703]
Carl is still not apparently available, or he would blog something.
Andreas
6-Jan-2012
[2704]
Anyone knows of a simple way to get to the binary encoding of a decimal! 
using just REBOL/Core (i.e. no struct!, no /library)?
Steeve
6-Jan-2012
[2705x2]
why don't you want ti use struct!, it simple enough ?
Ah! already left
Andreas
6-Jan-2012
[2707]
Because it doesn't work on /Core.
Steeve
6-Jan-2012
[2708]
don't want R3 neither ?
Andreas
6-Jan-2012
[2709]
Nope, then I'd ask in another channel :) R2/Core it is.