[英]reverse a vector in clojure (noob)
Hi I just starting with Clojure and I cannot manage to reverse a vector of integers. 嗨,我刚开始使用Clojure,我无法设法反转整数向量。
;generate a vector of random integers
(defn generate-rands
[x]
(vector (take x (repeatedly #(rand-int 100))))
)
;vector of integers
(def my-vector (generate-rands 10))
;reverse the vector of integers
(def my-vector-reversed (reverse my-vector))
;main
(defn main-app
[]
(println "My Vector: \t\t\t" my-vector)
(println "My Vector Reversed: \t" my-vector-reversed))
The output is 输出是
=> (main-app)
My Vector: [(14 49 29 3 66 7 60 60 34 19)]
My Vector Reversed: [((14 49 29 3 66 7 60 60 34 19))]
nil
#'startingclojure.app/main-app
=> (vector? my-vector-reversed)
false
Can someone kindly explain me why my-vector-reversed
is not a vector? 有人可以my-vector-reversed
解释为什么my-vector-reversed
不是矢量吗? And how can I reverse the content of 'my-vector'? 我怎样才能扭转'my-vector'的内容呢? Thanks 谢谢
Also, it's preferable to use rseq
instead of reverse
when you work with vector
or sorted-map
. 此外,当您使用vector
或sorted-map
时,最好使用rseq
而不是reverse
。 It has constant time, because they are indexed and can be efficiently walked in either direction. 它具有恒定的时间,因为它们被索引并且可以在任一方向上有效地行走。
from reverse's doc : 来自reverse的文档 :
Returns a seq of the items in coll in reverse order. 以相反的顺序返回coll中的seq项。 Not lazy. 不懒惰。
reverse turns anything into a seq, meaning, a list. 反向将任何东西变成seq,意思是列表。 in order to get back a vector you should turn it into a vector: 为了找回一个向量,你应该把它变成一个向量:
(into [] (reverse [1 2 3 4])) ; =>[4 3 2 1]
In your case, look at your "my-vector": [(14 49 29 3 66 7 60 60 34 19)] - its a vector containing a single element - a seq. 在你的情况下,看看你的“我的向量”:[(14 49 29 3 66 7 60 60 34 19)] - 它是一个包含单个元素的向量 - 一个seq。 so reversing it wouldnt change anything. 所以扭转它不会改变任何事情。 you should use the same technique to turn your seq into a vector: 你应该使用相同的技术将你的seq变成一个向量:
(defn generate-rands
[x]
(into [] (take x (repeatedly #(rand-int 100)))))
reverse
function returns always a seq
, not a vector. reverse
函数总是返回seq
,而不是向量。 You can again convert the result into a vector with something like: (apply vector (reverse [1 2 3]))
您可以再次将结果转换为具有以下内容的向量:( (apply vector (reverse [1 2 3]))
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