$loop() for dummies

Development Export
#1

I'm not a programmer, but I find the export configuration function in mp3tag to be quite powerful for maintaining and reporting on my podcast collection, and so I muddled through. What I've found through trial-and-error is you should think about the $loop more as a sort function. This is not based on any real knowledge, rather on my reading of the output from many dozens of my hand-built export configuration files.

The $loop parameter, the %album% in $loop(%album%), sorts your mp3tag listing before executing your export code. For example, $loop(%album%) sorts your mp3tag selection by album, then executes your export code line by line on the results.

$loop(%dummy%) would execute your code based on your last manual sorting operation. $loop(%album%)$loop(%title%) sorts your mp3tag listing first by title, then by album, and then executes your code (note the reverse order).

$loop()$loop()$loopend()$loopend() does NOT execute your code twice. It merely sorts twice then executes your code once. To execute code twice use $loop()...coding...$loopend() $loop()...coding...$loopend().

If you have an export configuration that should execute differently depending on how the mp3tag listing is sorted, then you should use %dummy% as the $loop parameter. For example, I use an export configuration to print out playlists. For podcasts that need to be listened to in order, I first sort manually by track and then run the export configuration. For podcasts that can be listened to in any order, I first sort manually by random.

This at least is how I see it. I welcome any clarifications.

Nested Loop Sorting Not Working?
#2

Did you know that the File menu has an extra function to generate playlists from the currently displayed lists (and selected files). So you don't have to create a separate report for playlists.

You did not mention the
$loop(%fieldname%,1) which sorts but outputs each item only once. This might be useful if you want to count certain occurrances. Or find similar but not totally equal entries.

#3

One can perhaps say so.

Another interpretation may be, that the first $loop() sorts by the value %ALBUM%, ...
and within this sorted workspace, ...
then the second $loop() sorts by the value %TITLE% within each related ALBUM.

If you apply $loop(%DUMMY%), then Mp3tag takes the current sequence of the selected files in the listview as the input.

If you apply $loop(%ALBUM%%TITLE%), then this may give other results than a nested $loop().

DD.20150813.2020.CEST

#4

Yes this is curious. There's a gap in my understanding of loops ... neither $loop(%album%%title%) nor $loop(%title%%album%) give the same result (sometimes) as $loop(%album%)$loop(%title%).

I'll think about this ...

rko

#5

Variables inside the loop are different (i.e. have different scope) from the ones outside the loop.
This simple code sets a variable before the loop and then changes its value inside the loop. Added second loop for better understanding. Run the export for few selected files.

$filename(test.txt,utf-8)
value=$put(val,$add($get(val),1))
$loop(%album%)value inside loop=$put(val,$add($get(val),1))$loopend()
value=$put(val,$add($get(val),1))
$loop(%album%)value inside loop=$put(val,$add($get(val),1))$loopend()

Someone would expect values to incremental in all script. Not exactly.
Output for 5 selected files would be:

value=1
value inside loop=1
value inside loop=2
value inside loop=3
value inside loop=4
value inside loop=5
value=2
value inside loop=6
value inside loop=7
value inside loop=8
value inside loop=9
value inside loop=10
Interesting. I find it odd but it is what it is.
It all depends on the design (intention).
edit: fixed typo ($endloop --> $loopend)