[chaley]

Originally Posted by ownedbycats

If it finds one unwanted identifier, it would then skip the rest. What should I use instead of if-thens?

If you want all the checks to be made then you should use a sequence of if-thens without the else. You would need to pass along the intermediate result.

NB: The template in #530 doesn't have the problem. For completeness, here is the version corrected for the error you mentioned in #531.

program:

	def do_one(ids, check_value, select_identifier):
		si = select(ids, select_identifier);
		if 
			!$#purchasesource==check_value && si
		then
			return list_difference (ids, strcat(select_identifier, si), ',')
		fi;
		return ids
	fed;

	ids = do_one($identifiers, "Amazon",'amazon');
	ids = do_one(ids, "Barnes & Noble", 'barnesnoble');
	ids = do_one(ids, "Kobo", 'kobo');
	ids = do_one(ids, "Baen", 'baen')