[itishappy]

Honestly both read about the same to me, and I'm largely unfamiliar with Clojure. The main difference appears to be the 3 `str` callouts, which appear extraneous as the following version works just the same:

    (defn color [word letter idx]
      (cond
        (= (nth word idx) letter) :green
        (str/includes? word letter) :yellow
        :else :gray))

Interesting that even with the `str` callouts removed, the function still appears to work on other datatypes such as:

    (def s (seq ("test1"))

A lazy sequence, but one Clojure still allows to be indexed over in O(1) time. That's probably what the `str` conversion was trying to speed up.

Python, meanwhile, fails on lazy input as it isn't indexable.

    word = (c for c in "test1")

I guess I'll be checking out Clojure this weekend.

[kazinator]

I'm guessing that str allow it to work when the inputs are symbols? So that they are compared as strings rather than by identity. There could be more than one symbol named "foo"; if you want those to compare the same, you can't use regular symbol equality.

Or possibly the code even uses non-symbols for some of the arguments. Suppose that letter is sometimes the integer 1.