什么是惯用的方法prePEND在Clojure的载体？ [英] What is the idiomatic way to prepend to a vector in Clojure?

问题描述

prepending到一个列表很简单：

Prepending to a list is easy:

user=> (conj '(:bar :baz) :foo)
(:foo :bar :baz)

附加到一个向量很简单：

Appending to a vector is easy:

user=> (conj [:bar :baz] :foo) 
[:bar :baz :foo]

我如何（地道）prePEND为向量，而取回一个载体？
这不起作用，因为它返回一个序列，而不是一个向量：

How do I (idiomatically) prepend to a vector, while getting back a vector? This does not work as it returns a seq, not a vector:

user=> (cons :foo [:bar :baz])     
(:foo :bar :baz)

这是丑陋的（IMVHO）：

This is ugly (IMVHO):

user=> (apply vector (cons :foo [:bar :baz])) 
[:foo :bar :baz]

请注意：我基本上只是希望有一个数据结构，我可以追加和prePEND来。追加到大名单应该有一个大的性能损失，所以我想的载体。

Note: I basically just want a datastructure that I can append and prepend to. Appending to large lists should have a large performance penalty, so I thought of vectors..

推荐答案

向量不会被设计为prepending。你只有为O（n）prePEND：

Vectors are not designed for prepending. You have only O(n) prepend:

user=> (into [:foo] [:bar :baz])
[:foo :bar :baz]

您需要的是最有可能是手指树。

What you want is most likely a finger tree.

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