继续在Clojure [英] Continuations in Clojure

问题描述

我读的地方有丰富的hickey说：

I read somewhere where rich hickey said:

我认为续约在理论上可能是整洁的
，练习

"I think continuations might be neat in theory, but not in practice"

我不熟悉clojure。

1. clojure有延续吗？

2.如果不是，你不需要继续吗？我看到很多很好的例子，特别是来自这个家伙。什么是替代方法？

3.如果是，是否有文档？

I am not familiar with clojure.
1. Does clojure have continuations?
2. If no, don't you need continuations? I have seen a lot of good examples especially from this guy. What is the alternative?
3. If yes, is there a documentation?

推荐答案

你必须区分两种不同的类型：

When talking about continuations, you’ll have to distinguish between two different kinds of them:

• 一类继承 - 继续支持深深地融入了语言（Scheme或Ruby）。

• First-class continuations – Continuation-support that is deeply integrated in the language (Scheme or Ruby). Clojure does not support first-class continuations.

继续传递风格（CPS） - CPS只是一种编码风格，任何支持匿名函数的语言允许这种风格（也适用于Clojure）。

Continuation-passing-style (CPS) – CPS is just a style of coding and any language supporting anonymous functions will allow this style (which applies to Clojure too).

示例：

-- Standard function
double :: Int -> Int
double x = 2 * x

-- CPS-function – We pass the continuation explicitly
doubleCPS :: Int -> (Int -> res) -> res
doubleCPS x cont = cont (2 * x)

; Call
print (double 2)

; Call CPS: Continue execution with specified anonymous function
double 2 (\res -> print res)

$ b b

阅读维基百科上的续篇。

我不认为继续对于一个好的语言是必要的，但是特别是在Haskell这样的功能语言中的第一类继承和CPS可能是非常有用的（智能回溯示例）。

I don’t think that continuations are necessary for a good language, but especially first-class continuations and CPS in functional languages like Haskell can be quite useful (intelligent backtracking example).

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