Catch missing value

Scripting Forums AppleScript | Mac OS X
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#1

Im sure this will have been done better by some one before. In trying to help someone here in forum a problem I’ve had before came up again when trying a few tests.
Here is the scenario say I want 2 lists from a folder.
List 1 to contain files of (known creator type or missing value) + Extension
List 2 to contain files of (known creator type) + Extension
The second list I can get to work but my questions are have I gone about this the right way? Would “file type” be better than “Extension” as I would need to list .jpeg & .jpg? and can I quote a missing value? to one of my property lists. Hope I’ve made some sort of sense of this!!!

property CreatorType : {"", "8BIM"} -- How do I get missing value to this?
property OtherTypes : {"ART5", "CARO", "XPR3"}
property FileTypeList : {"8BIM", "BMP ", "EPSF", "GIFf", "JPEG", "PICT", "PCX ", "PNGf", "8BPS", "PXR ", "PRAW", "SCRN", "..CT", "TPIC", "PDF ", "8BPS", "TIFF"}
property ExtensionList : {"", "ai", "bmp", "eps", "gif", "jpg", "pct", "pcx", "png", "psd", "pxr", "raw", "rsr", "sct", "tga", "pdf", "psd", "tif"}
--
set inputFolder to choose folder with prompt "Where's the images folder?"
tell application "Finder"
	set MyImageFiles to (every file of entire contents of inputFolder) as alias list
end tell
--
set PSformats to {}
tell application "Finder"
	repeat with this_item in MyImageFiles
		set x to properties of this_item
		if name extension of this_item is in ExtensionList and creator type of this_item is in CreatorType then copy (this_item as string) to end of PSformats
	end repeat
end tell
return PSformats
--
set RasterThis to {}
tell application "Finder"
	repeat with this_item in MyImageFiles
		set y to properties of this_item
		if name extension of this_item is in ExtensionList and creator type of this_item is in OtherTypes then copy (this_item as string) to end of RasterThis
	end repeat
end tell
return RasterThis
#2

missing value is an AppleScript word pair - no quotes.

#3

Adam, by word pair do you mean that this would work? Never thought to drop the quotes but had noticed it like that in the event log.doh I will give it a try thanks

property CreatorType : {missing value, "8BIM"}
#4

missing value is a constant value

#5

it’s not that important

#6

I don’t know if it will work in your specific application, but it’s a very easy way to operate on lists in general.

set myLst to {"eeny", "meany", "miney", "moe"}
set item 3 of myLst to missing value --> {"eeny", "meany", missing value, "moe"}
set myLst to myLst's strings --> {"eeny", "meany", "moe"}

0r

set myLst to {1, 2, 3, 4, 5, 6}
set item 3 of myLst to missing value
set myLst to myLst's integers --> {1, 2, 4, 5, 6}