Brian - your diagnosis is spot-on. I neglected to test the verb in a clean
J session before I posted it. I apologize.
The names 'prefix' and 'suffix' on the line that assigns 'fn' should be
spelled 'pfx' and 'sfx' respectively. Corrected (and tested!) verb below.
-Dan
PS: For those interested, the stack error was a cascade effect of my
oversight.
Since prefix and suffix were undefined, when fn was assigned, it got defined
as a (meaningless) verb. In turn, this caused pn to be defined as a verb,
and subsequently redefined in terms of itself.
So, when the final line was executed, J attempted to call pn as a verb on
the argument ,.<'.',sfx, causing an infinite recursion, and ultimately the
stack error.
flipOddPages=:verb define
'comb png' flipOddPages y
:
NB.y=directory to scan, x=file prefix and suffix
'pfx sfx'=.2 {. (;:^:(0=L.) x),<'png'
dir =. (,'\'-.{:)y
NB. Scan directory
fn =. {. |: 1!:0 jpath dir,pfx,'*',sfx
NB. Zero-fill here will convert comb.png to comb 0.png
NB. The increments account for the space after comb and
NB. the dot before png respectively.
pn=.0 ".&> (1+#pfx) }.&.> (-1+#sfx)}.&.> fn
NB. Reverse order of odds
pn=.(+ 2&| * #-+:) pn
NB. Table of old-filename, new-filename
fn ,. <@;"1 (<pfx,' '),.(":&.> pn),.<'.',sfx
)
flipOddPages '~temp\archive1'
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Brian Schott
Sent: Saturday, December 14, 2013 11:56 AM
To: Chat forum
Subject: Re: [Jchat] Fwd: Archive j
Dan,
Thank you very much. That looks terrific.
I am having a little trouble making it work on my Mac. Do you see the
problem based on the error message below?
Btw, I am suspicious of the noun `suffix` because it doesn't look like it is
defined. I can debug further myself, but I thought you would like to know my
progress.
'combined png' flipOddPages '/Users/brian/Documents/combined\ not'
|stack error: pn
| fn,.<@;"1(<pfx,' '),. (":&.>pn),.<'.',sfx
On Sat, Dec 14, 2013 at 11:28 AM, Dan Bron <[email protected]> wrote:
> Saw your message come in and have just been noodling around with the
> idea of reversing only the odd pages. Does the following help?
>
> flipOddPages=:verb define
> 'comb png' flipOddPages y
> :
> NB.y=directory to scan, x=file prefix and suffix
> 'pfx sfx'=.2 {. (;:^:(0=L.) x),<'png'
> dir =. (,'\'-.{:)y
>
> NB. Scan directory
> fn =. {. |: 1!:0 jpath dir,prefix,'*',suffix
>
> NB. Zero-fill here will convert comb.png to comb 0.png
> NB. The increments account for the space after comb and
> NB. the dot before png respectively.
> pn=.0 ".&> (1+#pfx) }.&.> (-1+#sfx)}.&.> fn
>
> NB. Reverse order of odds
> pn=.(+ 2&| * #-+:) pn
>
> NB. Table of old-filename, new-filename
> fn ,. <@;"1 (<pfx,' '),.(":&.> pn),.<'.',sfx
> )
>
> Here, if you had a subdirectory in your J temp folder named
> 'archive1', with
> 10 files in it ('comb.png' plus 'comb 1.png' through 'comb 9.png'),
> you'd call it like this:
>
> flipOddPages '~temp\archive1'
> +----------+----------+
> |comb 1.png|comb 9.png|
> +----------+----------+
> |comb 2.png|comb 2.png|
> +----------+----------+
> |comb 3.png|comb 7.png|
> +----------+----------+
> |comb 4.png|comb 4.png|
> +----------+----------+
> |comb 5.png|comb 5.png|
> +----------+----------+
> |comb 6.png|comb 6.png|
> +----------+----------+
> |comb 7.png|comb 3.png|
> +----------+----------+
> |comb 8.png|comb 8.png|
> +----------+----------+
> |comb 9.png|comb 1.png|
> +----------+----------+
> |comb.png |comb 0.png|
> +----------+----------+
>
> The resulting table is a mapping of original filenames to corrected
> filenames, where the order of the odd pages has been reversed (and the
> first page has been made consistent by adding an index, 0). Actually
> renaming the files is left as an exercise for the reader (but isn't
> difficult).
>
> While packaging this up for re-use, I noticed it had a very familiar
> structure.
>
> read filenames
> parse filenames (drop pfx+' ', sfx+'.')
> multiply page number by two
> subtract count
> residue page number by two
> format filenames (tack pfx+' ',sfx+'.')
> write filenames
>
> Now, I don't think it'd be worthwhile to rewrite the verb using under,
> especially since it's got side-effects and the central &. is a bit
> iffy, but I thought it interesting nonetheless.
>
> (Or maybe if one spends too much time with J, he begins to see unders
> everywhere :)
>
> -Dan
>
>
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of Brian Schott
> Sent: Saturday, December 14, 2013 10:00 AM
> To: Chat forum
> Subject: [Jchat] Fwd: Archive j
>
> I have been studying ways to digitally archive old paper reports using
> a one-sided scanner with an automatic paperfeed. Two options have
> occurred to me.
>
> One. Scan to a single PDF file,
> Two. Scan to a folder containing multiple PNG files.
>
> The options are very similar except that the PDF mode seems to take
> considerably more disk space.
>
> Both methods suffer slightly when the original documents are two-sided
> because either the pages are out of order (in the PDF) or the
> numbering of the individual files in the folder is out of order.
>
> I would like to implement a routine for the second option that would
> rename the multiple PNG files. So I have developed some simple J verbs
> to create the indexes of the filenames, but I do not know how to
> associate those results with the original files and rename the
> original files correctly in the case of two-sided originals.That is
> where I would like some help especially in knowing what part of the
> task can be done in J and what part is done in unix batch files.
>
> Notice in the "typical" example below of four pages that the pages of
> the second side are in the reverse of the correct order and that the
> very first page does not have a number associated with it.
>
> server:Documents brian$ ls -l combined\ not total 872
> -rw-r--r-- 1 brian staff 88517 Dec 14 09:13 combined 1.png
> -rw-r--r-- 1 brian staff 119690 Dec 14 09:13 combined 2.png
> -rw-r--r-- 1 brian staff 129123 Dec 14 09:13 combined 3.png
> -rw-r--r-- 1 brian staff 100494 Dec 14 09:13 combined.png
> server:Documents brian$ ls -l combined.pdf -rw-r--r--@ 1 brian staff
> 971300 Dec 12 08:22 combined.pdf
>
>
> Below are the J verbs for creating indexes based on the number of
> files in a directory.
>
> nodd=: >.@-:
> neven=: <.@-:
> odd=: >:@+:@i.@nodd
> even=: 2+|.@:+:@i.@neven
> zero=: '0'&,@":"0
>
> Note 'some test cases'
> <@:even"0] 0 1 2 3 4
> <@:odd"0] 0 1 2 3 4
> zero odd 4
> zero even 3
> zero even 0
> 1&|. zero (odd,even) 4 NB. this would be most like
> NB. a production case because it would NB. match the order of the file
> list in the original ls
> )
>
> Thanks,
>
> ---
> (B=)
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm
>
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm
>
--
(B=) <-----my sig
Brian Schott
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