[chaley]

Originally Posted by capink

@chaley: I am having a little problem with the for loop, relating to a new template function I've added to the plugin. The function is called category_items(). It works as follows

program:
    category_items('#genre')

This would return all the #genre tags.

It can also take second optional arg to limit the result to set of book_ids

program:
    book_ids = from_selection('id');
    category_items('#genre',book_ids)

from_selection() can be replaced with from_search() to achieve the same result. I've updated both to accept 'id' as column name and return a list of book_ids.

Good idea. I have used the calibre built-in version of this function many times. Are you using it to do the implementation? It is calibre.db.cache.get_categories. It supports a list of book ids, does caching, and has several other optimizations. It returns a dict

['lookup_name': set_of_values, ...]

The tag browser uses this function to build the category list.

The problem arise when I run the new function on a field containing names like 'authors'. I have to return a list separated with an ampersand, because author names can have commas in them. The documentation says the for loop will only accept a comma separated list of values. Can this modified to allow the user to somehow choose a different separator, maybe by setting a variable before running the for loop.

I can do this. The big question is how? What I would prefer to do is extend the language for the for statement, making its grammar

'for' varname 'in' expression ['separator' expression] ':'

Specifying the separator is optional. OK with you?

Another thing: I started making another function top_category_items() that is the same to the above function, but only extracts the top hierarchy level. I then starting having doubt, because I thought maybe combining the category_items() with subitem() would be a better way to achieve this and also offers more possibilities. The problem here is with that approach, I have to remove duplicates myself. It can be done using template but a lot of hassle. I ran recently into this problem in this template. The solution would be to add a uniq() template that removes duplicates from a list. I can easily add this, but I think it might be better to be included in the template builtin functions. Would you be willing to add something like this? I not, I will add to the plugin.

You can already do exactly this with list_union, as in

list_union('', list_to_remove_duplicates, sep)

However, I realize that this use of list_union is rather esoteric, so I will add the function

list_remove_duplicates(list, sep)

If you think that list_uniq(), or perhaps list_unique(), is a better name than I can use that.