more separation of concerns.

src/cljc/auto_ap/utils.cljc

@@ -17,3 +17,12 @@
        (conj xs x)))
    []
    existing))
+
+(defn replace-by [xs f x]
+  (mapv
+   (fn [t]
+     (if (= (f t) (f x))
+       x
+       t))
+   xs))
+