生成长度相同的N的矢量N

Question

我想生成一个给定项目和计数的相同项目的矢量。这似乎是一个比循环更容易完成的事情。任何让这个功能更紧密/简化的想法？

;take an object and a nubmer n and return a vector of those objects that is n-long 
(defn return_multiple_items [item number-of-items] 
    (loop [x 0 
      items [] ] 
     (if (= x number-of-items) 
      items 
      (recur (+ x 1) 
        (conj items item))))) 

>(return_multiple_items "A" 5) 
>["A" "A" "A" "A" "A"] 
>(return_multiple_items {:years 3} 3) 
>[{:years 3} {:years 3} {:years 3}] 

Answer 1

有一个内置的功能repeat特别是对这种情况下设计：

> (repeat 5 "A") 
("A" "A" "A" "A" "A") 

正如你可以看到，它产生相同的元素的序列。如果你需要一个载体，可以与vec CONVER吧：

> (vec (repeat 5 "A")) 
["A" "A" "A" "A" "A"] 

Answer 2

的repeat功能在这里派上用场：

user> (defn return-multiple-items [item how-many] 
     (vec (repeat how-many item))) 
#'user/return-multiple-items 

user> (return-multiple-items "A" 5) 
["A" "A" "A" "A" "A"] 

Answer 3

user> (into [] (repeat 5 "A")) 
["A" "A" "A" "A" "A"] 

user> (into [] (repeat 3 {:years 3})) 
[{:years 3} {:years 3} {:years 3}]