I very much like the "Koans" approach to grabbing the basics of programming languages fundamentals. I would love if HackerRank included language-specific funct

I very much like the "Koans" approach to grabbing the basics of programming languages fundamentals. I would love if HackerRank included language-specific functions and methods that any hacker wanting to claim mastery of that language should know. For example, I would guess knowing map, reduce, filter in Clojure is probably something anyone who claims to be a Clojure hacker should be able to do at a whiteboard. In SQL, you better know inner and outer joins, insert from a table to different table, update one table with data from another table, and at least be able to talk a little about analytic functions (with data windows). Essentially, I want the concept of "The Little Schemer" in your challenges, both for concepts and specific languages.