Today I revisited this exercise from the Coursera Scala course that I did some time ago using the Advanced Student Language:
I refactored it to define the helper function f inside balanced-parentheses?.
Since it is not allowed to have nested function definitions in Advanced Student Language (it's in Racket), I defined the function using letrec and a lambda.
I had forgotten how many parentheses a cond needs in Advanced Student Language. In that sense Clojure is far more convenient.