unpack in incrementing variables

GrandFather has asked for the wisdom of the Perl Monks concerning the following question:

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Re: unpack in incrementing variables by davido (Cardinal) on Oct 14, 2005 at 02:32 UTC
It seems like you want something like this: `for ( 0 .. 32768 ) { print unpack( "B16", pack( "n", $_ ) ), "\n"; }` [download] Of course that produces a LOT of output, but it will produce bitstrings in contiguous order, most significant digit at the 'left', and least significant at the 'right'. One problem that it seemed like you were running into was the difference between ascending and descending bit order, combined with the difference between big-endian and little-endian packed integers. There's some documentation on all this in pack, but a more thorough discussion in perlpacktut. As for the question of why the iteration values in your foreach loop are being stringified, that can be explained in the documentation for unpack: unpack does the reverse of pack: it takes a string and expands it out into a list of values. (In scalar context, it returns merely the first value produced.) The key is that it treats its second arg as a string. Dave	[reply] [d/l]
Re: unpack in incrementing variables by demerphq (Chancellor) on Oct 14, 2005 at 07:54 UTC
As you said, use (s)printf. (printf doesnt respect -l so this looks a touch more clumsy than it needs to). `D:\dev>perl -e "printf '%08b%s',$_,$/ for 1..10" 00000001 00000010 00000011 00000100 00000101 00000110 00000111 00001000 00001001 00001010` [download] Unpack operates on strings not on integers so you need to ensure that chr(10) is passed in and not '10'. `D:\dev>perl -le "print unpack 'B*',chr($_) for 1..10" 00000001 00000010 00000011 00000100 00000101 00000110 00000111 00001000 00001001 00001010` [download] --- $world=~s/war/peace/g	[reply] [d/l] [select]
Re^2: unpack in incrementing variables by GrandFather (Saint) on Oct 14, 2005 at 09:38 UTC
Thank you. At last the answer to the question I actually asked. The question was why, not how. The answer is "Unpack operates on strings not on integers". Perl is Huffman encoded by design.	[reply]
Re^3: unpack in incrementing variables by demerphq (Chancellor) on Oct 14, 2005 at 09:44 UTC
I think people were inclined to show the how because the why is in the docs: unpack TEMPLATE,EXPR "unpack" does the reverse of "pack": it takes a string and expands it out into a list of values. (In scalar context, it returns merely the first value produced.) But I did it because i hadnt had my coffee before I posted (was waiting for it finish being made) and didnt read the question properly. Luckily the coffee was finished just after I hit submit so I realized the error and fixed it right after. :-) --- $world=~s/war/peace/g	[reply]
Re^4: unpack in incrementing variables by GrandFather (Saint) on Oct 14, 2005 at 10:31 UTC
Re^3: unpack in incrementing variables by Roy Johnson (Monsignor) on Oct 14, 2005 at 17:59 UTC
The question was why, not how. The question "Is it possible to...?" includes an implicit "How?" Answering such question with a simple "yes" is generally seen as teasing. Caution: Contents may have been coded under pressure.	[reply]
Re: unpack in incrementing variables by ikegami (Patriarch) on Oct 14, 2005 at 01:58 UTC
`print unpack ('B16', pack('I', $_))."\n" for (0..10);` [download]	[reply] [d/l]
Re^2: unpack in incrementing variables by GrandFather (Saint) on Oct 14, 2005 at 02:14 UTC
Close, but no banana. `print unpack ('B16', pack('I', $_))."\n" for (250..260); 1111101000000000 1111101100000000 1111110000000000 1111110100000000 1111111000000000 1111111100000000 0000000000000001 0000000100000001 0000001000000001 0000001100000001 0000010000000001` [download] which is not what I would like either. Besides, the question was why, not how. I have a how. Perl is Huffman encoded by design.	[reply] [d/l]
Re^3: unpack in incrementing variables by GrandFather (Saint) on Oct 14, 2005 at 02:21 UTC
Counter intuitively (for me at least): `print unpack ('B16', pack('n', $_))."\n" for (250..260); 0000000011111010 0000000011111011 0000000011111100 0000000011111101 0000000011111110 0000000011111111 0000000100000000 0000000100000001 0000000100000010 0000000100000011 0000000100000100` [download] the "network" format (big endian) does what I want on a little endian (Windows) system. Perl is Huffman encoded by design.	[reply] [d/l]
Re^4: unpack in incrementing variables by ikegami (Patriarch) on Oct 14, 2005 at 02:32 UTC
Re: unpack in incrementing variables by pg (Canon) on Oct 14, 2005 at 02:00 UTC
00110000 is 48, and that's the ASCII code for '0'. That's the explanation for your first line, the rest are the same, and the last line represents two characters: '1' and '0'. So that's expected with the code you have.	[reply]
Re: unpack in incrementing variables by EvanCarroll (Chaplain) on Oct 14, 2005 at 02:18 UTC
Might better suit you: `perl -e'printf("%08b\nb", $_) for (0..10);'` There is also a sprintf, though it probably a little slower than unpack. Evan Carroll www.EvanCarroll.com	[reply] [d/l]