Redefining a let'd variable in Clojure loop

Question

OK. I\'ve been tinkering with Clojure and I continually run into the same problem. Let\'s take this little fragment of code:

(let [x 128]
  (while (> x 1)
            


        

Answer 1

Vars (that's what you get when you "def" something) aren't meant to be reassigned (but can be):

user=> (def k 1)
#'user/k
user=> k
1

There's nothing stopping you from doing:

user=> (def k 2)
#'user/k
user=> k
2

If you want a thread-local settable "place" you can use "binding" and "set!":

user=> (def j) ; this var is still unbound (no value)
#'user/j
user=> j
java.lang.IllegalStateException: Var user/j is unbound. (NO_SOURCE_FILE:0)
user=> (binding [j 0] j)
0

So then you can write a loop like this:

user=> (binding [j 0]
         (while (< j 10)
           (println j)
           (set! j (inc j))))
0
1
2
3
4
5
6
7
8
9
nil

But I think this is pretty unidiomatic.