在 Clojure 中延迟构建集

发布于 2024-11-01 16:01:48 字数 449 浏览 4 评论 0原文

我已经开始学习 clojure，但我很难理解某些概念。例如，我在这里想要做的是获取此函数并将其转换，以便它延迟调用 get-origlabels。

(defn get-all-origlabels []
    (set (flatten (map get-origlabels (range *song-count*)))))

我的第一次尝试使用了递归，但炸毁了堆栈（song-count 约为 10,000）。我不知道如何用尾递归来做到这一点。

get-origlabels 每次调用时都会返回一个集合，但值通常在调用之间重复。 get-origlabels 函数实际上的作用是读取一个文件（从 0 到 song-count-1 的每个值都有一个不同的文件）并返回存储在其中的单词集合。

任何指示将不胜感激！

谢谢！ -菲利普

原文

I've started to learn clojure but I'm having trouble wrapping my mind around certain concepts. For instance, what I want to do here is to take this function and convert it so that it calls get-origlabels lazily.

(defn get-all-origlabels []
    (set (flatten (map get-origlabels (range *song-count*)))))

My first attempt used recursion but blew up the stack (song-count is about 10,000). I couldn't figure out how to do it with tail recursion.

get-origlabels returns a set each time it is called, but values are often repeated between calls. What the get-origlabels function actually does is read a file (a different file for each value from 0 to song-count-1) and return the words stored in it in a set.

Any pointers would be greatly appreciated!

Thanks!
-Philip

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看透却不说透 2024-11-08 16:01:48

你可以使用mapcat得到你想要的东西。我相信将它放入实际的 Clojure 集合中将会消除它的惰性，正如 (take 10 (set (iterate inc 0))) 尝试在 take 之前实现整个集合的事实所证明的那样10.

(distinct (mapcat get-origlabels (range *song-count*)))

这会给你一个惰性序列。您可以通过执行类似的操作来验证这一点，从无限序列开始：

(->> (iterate inc 0)
     (mapcat vector)
     (distinct)
     (take 10))

您最终会得到一个 seq，而不是一个集合，但由于听起来您确实想要在这里懒惰，所以我认为这是最好的。

You can get what you want by using mapcat. I believe putting it into an actual Clojure set is going to de-lazify it, as demonstrated by the fact that (take 10 (set (iterate inc 0))) tries to realize the whole set before taking 10.

(distinct (mapcat get-origlabels (range *song-count*)))

This will give you a lazy sequence. You can verify that by doing something like, starting with an infinite sequence:

(->> (iterate inc 0)
     (mapcat vector)
     (distinct)
     (take 10))

You'll end up with a seq, rather than a set, but since it sounds like you really want laziness here, I think that's for the best.

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孤芳又自赏 2024-11-08 16:01:48

这可能有更好的堆栈行为

(defn get-all-origlabels []
    (reduce (fn (s x) (union s (get-origlabels x))) ${} (range *song-count*)))

This may have better stack behavior

(defn get-all-origlabels []
    (reduce (fn (s x) (union s (get-origlabels x))) ${} (range *song-count*)))

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欢你一世 2024-11-08 16:01:48

我可能会使用类似的东西：

(into #{} (mapcat get-origlabels (range *song-count*)))

一般来说，“into”在构建 Clojure 数据结构时非常有用。我的脑海中浮现出这样的画面：传送带（一个序列）将一堆随机物体放入一个大桶（目标集合）中。

I'd probably use something like:

(into #{} (mapcat get-origlabels (range *song-count*)))

In general, "into" is very helpful when constructing Clojure data structures. I have this mental image of a conveyor belt (a sequence) dropping a bunch of random objects into a large bucket (the target collection).

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