Template: sum of multiple integers from other columns

[Quuzuu]

Suppose in an attempt to better rate my books, I created 4 custom columns: 'story', 'characters', 'writing', 'ending', each an integer between 1-10.

Then I'd like to add another column called 'total_score', which is the sum of the above. How should I build the template?

(General Program Mode is preferred, if possible)

Thanks!!

[Quuzuu]

I tried something like:
program: field(#'story') + field(#'characters') + field(#'writing') + field(#'ending')
which didn't work.

I also tried program: add(x, y), but it only accept 2 arguments, which could work, but seems a little messy.

[Quuzuu]

Update: my current solution (wonder if there's a cleaner way):

program:
r = 0;
r = add(r, field('#story'));
r = add(r, field('#characters'));
r = add(r, field('#writing'));
r = add(r, field('#ending'));
floor(r);

[chaley]

In the next version of calibre (5.10 probably) add() and multiply() accept a variable number of arguments. Thus, once released your solution can be written as

program:
    floor(add(field('#story'), field('#characters'), field('#writing'), field('#ending')))

To head off questions: I changed add() and multiply() because the operations are commutative, giving the same answer regardless of order of evaluation, while subtract and divide are not. I don't want to worry about guaranteeing the order of evaluation within the function.

[Quuzuu]

Thanks so much!