digium requires you to sign a license agreement https://issues.asterisk.org/jira/secure/DigiumLicense.jspa

that's the dream but there are some companies which send out their pre-baked "weekend projects" after the initial hr screening and I'm talking about large corporations (the new york times for example) which isn't terrible at first but results in lots of trying to look up what practices the company in question follows and prefers and what they are actually looking for

personally I really need human feedback rather then 8 hours at my desk guessing and searching for what's being looked for

it's one of those situations where I see the value for the interviewer but as the applicant it's completely sucks especially when you have 4 sample projects to write at home while juggling phone interviews and you know having a life/job

I don't fully understand the direction you were going with some of the solutions, something like this would work no?

(defn digits [num] (let [ x (map str (str num)) s (map read-string x)] (apply + (map #(* % %) s))))

I do think the interviewer should have pointed you in the right direction or offer some sort of hint to gain an understanding of how comfortable you are with the language rather then just having you fumble around but depending on the role they were hiring for these questions and this practice don't seem bad to me