在 Clojure 中遍历 Map 时如何保持顺序？

Question

我有以下地图：

(def tmp-cust-data {:customers
                    {:january [1 0 2 0 3 0 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]
                     :february [0 1 0 2 0 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]
                     :march [0 0 0 0 0 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]
                     :april [1 0 2 0 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ]
                     :may [1 0 2 0 3 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]
                     :june [1 0 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]
                     :july [1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]
                     :august [1 0 2 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]
                     :september [1 0 2 0 3 0 4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]
                     :october [1 0 2 0 3 0 4 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]
                     :november [1 0 2 0 3 0 4 0 5 0 6 0 7 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ]
                     :december [1 0 2 0 3 0 4 0 5 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]}})

当我在该地图上执行类似 doseq 的操作时，我注意到顺序未保留：

(doseq [[k v] (:customers tmp-cust-data)] (println k))

是否有适当的方法在保留顺序的同时迭代地图？

Answer 1

使用地图的有序版本。

(def tmp-cust-data {:customers
                    (flatland.ordered.map/ordered-map
                        [[:january [1 0 2 0 3 0 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]]
                         [:february [0 1 0 2 0 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]]
                         [:march [0 0 0 0 0 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]]
                         [:april [1 0 2 0 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]]
                         [:may [1 0 2 0 3 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]]
                         [:june [1 0 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]]
                         [:july [1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]]
                         [:august [1 0 2 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]]
                         [:september [1 0 2 0 3 0 4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]]
                         [:october [1 0 2 0 3 0 4 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]]
                         [:november [1 0 2 0 3 0 4 0 5 0 6 0 7 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]]
                         [:december [1 0 2 0 3 0 4 0 5 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]]])})

Answer 2

根据定义，哈希映射本质上是无序的。您可以选择键的顺序，然后您可以按顺序迭代这些键并访问散列映射值，但散列映射本身不可能有“顺序”。

在 Clojure 中遍历 Map 时如何保持顺序？

How to maintain order when iterating over a Map in Clojure?

clojure