集合与序列的Clojure等式 [英] Clojure equality of collections with sequences
问题描述
我注意到Clojure（1.4）似乎很乐意考虑等于相同向量的 seq 的向量，但是相同的不适用于地图：
I noticed that Clojure (1.4) seems to be happy to consider vectors equal to the seq of the same vector, but that the same does not apply for maps:
(= [1 2] (seq [1 2]))
=> true
(= {1 2} (seq {1 2}))
=> false
为什么 = 的行为应为
推荐答案
Clojure的 = 可以认为是分两步执行比较：
Clojure's = can be thought of as performing its comparisons in two steps:
-
检查所比较事物的类型是否属于相同的平等分区，那是一类类型，其成员可能相等（取决于像给定数据结构的确切成员之类的东西，但不取决于分区中的特定类型）；
Check if the types of the things being compared belong to the same "equality partition", that is a class of types whose members might potentially be equal (depending on things like the exact members of a given data structure, but not the particular type in the partition);
如果是这样，请检查所比较的事物是否实际上相等。
If so, check if the things being compared actually are equal.
一个这样的相等分区是： 顺序事物。向量被认为是顺序的：
One such equality partition is that of "sequential" things. Vectors are considered sequential:
(instance? clojure.lang.Sequential [])
;= true
各种类型的序列如下：
(instance? clojure.lang.Sequential (seq {1 2}))
;= true
因此，当（且仅当）其对应元素相等时，向量才被视为等于序列。
Therefore a vector is considered equal to a seq if (and only if) their corresponding elements are equal.
（请注意，（seq {}）产生 nil ，这是 not 顺序的，并且比较不等于 （）， [] 等）
(Note that (seq {}) produces nil, which is not sequential and compares "not equal" to (), [] etc.)
在另一方面，映射构成它们自己的相等分区，因此，虽然哈希映射可能被视为等于排序的映射，但永远不会将其视为等于序列。特别是，它不等于其条目的seq，这就是（seq some-map）产生的。
On the other hand, maps constitute an equality partition of their own, so while a hash map might be considered equal to a sorted map, it will never be considered equal to a seq. In particular, it is not equal to the seq of its entries, which is what (seq some-map) produces.
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