在J中设置用户定义动词的等级

Question

Here's a function to calculate the digital sum of a number in J:

digitalSum =: +/@:("."0)@":

If I use b. to query the rank of this verb, I get _ 1 _ , ie, infinite. (We can ignore the dyadic case since digitalSum is not dyadic.)

I would like the monadic rank of this verb to be 0, as reported by b. . The only way I know of to do this is to use a "shim", eg,

ds =: +/@:("."0)@":
digitalSum =: ds"0

This works great, but I want to know whether it's the only way to do this, or if there's something else I'm missing.

Clarification

I just discovered how to change the rank of a verb that's defined thus:

digits =: 3 : 0 "0
    "."0@": y
)

Notice the "0 after the declaring 3 : 0 . You can put any adverb or conjunction you wish, and it will be applied to the verb as a whole. Pretty cool stuff!

Answer 1

digitalSum =: (+/@:("."0)@":)"0 is how I would define it as well. Using " to change rank is pretty standard and works on parenthesized tacit trains.