Question

Does memoize keep track of changes to binding which may make returning a computation it has stored incorrect?

For example if I have a function foo such as:

(defn foo [bar baz]
 ...
   (let [config-val *config-val*]
    ...)
 )

which I contain within a binding so I can change the value of *config-val*, does memoizing it mean that if I change the value of *config-val*, but not the parameters to it that it will not recompute the value of the function? Instead it will give me the value of the function with the old configuration?

Answer 1

In Clojure 1.3.0 memoize doesn’t keep track of rebinding.

user=> (def ^:dynamic *x* 5)
#'user/*x*
user=> (def f (memoize #(+ *x* %)))
#'user/f
user=> (f 1)
6
user=> (binding [*x* 6] (f 1))
6
user=> (binding [*x* 7] (f 1))
6

Additionally,

user=> (binding [*x* 7] (f 3))
10
user=> (f 3)
10
user=> *x*
5