[capink]

Originally Posted by chaley

[/CODE]I used the keyword 'separator' to remove some ambiguity in the language parser.

That makes senese. It is now working for me.

program:
	book_ids = from_selection('id');
	all_authors = category_items('authors',book_ids);
	res = '';
	for a in all_authors separator '&':
		ratings = from_search('rating', strcat('rating:true and author:"=', a, '"'));
		if ratings then
			avg = divide(mean(ratings), 2);
			res = list_union(res, strcat(a, ':', avg), ',')
		fi
	rof;
	res

Using all authors without restricting them using from_search() or from_selection() on large libraries is not recommended as it is verrrrrrry slow.

Originally Posted by chaley

Note that the 'thing' following the keyword is an arbitrary expression.

Wow. I will sure come up with a use for that sometime in the future.