英文:
Apply a key as a function to its value
问题
假设你有一张特殊的地图，其中每个键可能代表一个Clojure核心函数：{:inc 1 :dec 2 :identity "three"}你想要写什么来将每个键（作为函数）应用于它自己的值？输出应该得到类似这样的结果：(2 1 "three")这段代码未能产生我期望的结果：user=> (def mm {:inc 1 :dec 2 :identity "three"})user=> (map #((symbol (first %)) (get % 1)) mm)(nil nil nil)
英文:
Suppose you have a peculiar map where each key might represent a Clojure core function:
{:inc 1 :dec 2 :identity "three"}
What would you write to apply each key (as a function) to its own value?
Output should yield something like:
(2 1 "three")
This code fails to produce what I expect:
user=> (def mm {:inc 1 :dec 2 :identity "three"})user=> (map #((symbol (first %)) (get % 1)) mm)(nil nil nil)
答案1
得分: 1
用 resolve 将符号包装起来可以解决这个问题：
(resolve (symbol (...)))
更详细的解释请查看这里：https://stackoverflow.com/a/63208807/4903731
以下任何一种方式都会产生所需的输出：
(def mm {:inc 1 :dec 2 :identity "three"})(map (fn [%] ((resolve (symbol (key %))) (val %))) mm)(map #((resolve (symbol (key %))) (val %)) mm)(map #((resolve (symbol (first %))) (get % 1)) mm)
英文:
Wrapping the symbol with resolve solves this problem:
(resolve (symbol (...)))
More detailed explanation here: https://stackoverflow.com/a/63208807/4903731
Any of the following produce the desired output:
(def mm {:inc 1 :dec 2 :identity "three"})(map (fn [%] ((resolve (symbol (key %))) (val %))) mm)(map #((resolve (symbol (key %))) (val %)) mm)(map #((resolve (symbol (first %))) (get % 1)) mm)
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