如何在Clojure脚本数据结构中进行搜索和替换？

Question

I would like to have a search and replace on the values only inside data structures:

(def str [1 2 3 
              {:a 1 
               :b 2 
               1  3}])

and

(subst  str  1  2) 

to return

[2 2 3 {:a 2, :b 2, 1 3}]

Another example:

(def str2  {[1 2 3] x, {a 1 b 2} y} )

and

(subst  str2  1  2) 

to return

{[1 2 3] x, {a 1 b 2} y}

Since the 1's are keys in a map they are not replaced

Answer 1

One option is using of postwalk-replace :

user> (def foo [1 2 3 
              {:a 1 
               :b 2 
               1  3}])
;; => #'user/foo
user> (postwalk-replace {1 2} foo)
;; => [2 2 3 {2 3, :b 2, :a 2}]

Although, this method has a downside: it replaces all elements in a structure, not only values. This may be not what you want.

---

Maybe this will do the trick...

(defn my-replace [smap s]
  (letfn [(trns [s]
            (map (fn [x]
                   (if (coll? x)
                       (my-replace smap x)
                       (or (smap x) x)))
                 s))]
    (if (map? s)
      (zipmap (keys s) (trns (vals s)))
      (trns s))))

Works with lists, vectors and maps:

user> (my-replace {1 2} foo)
;; => (2 2 3 {:a 2, :b 2, 1 3})

...Seems to work on arbitrary nested structures too:

user> (my-replace {1 2} [1 2 3 {:a [1 1 1] :b [3 2 1] 1 1}])
;; => (2 2 3 {:a (2 2 2), :b (3 2 2) 1 2})