构造quines(自我复制功能) [英] Constructing quines (self-reproducing functions)

问题描述

任何人都可以构造一个quine(一个程序，它会生成自己的源文本的副本作为其完整输出": http://www.nyx.net/~gthompso/quine.htm )中的R? ([quine]标签在Python，Java等中引出了很多示例，但在R中显然没有.)

Has anyone constructed a quine ("A program that generates a copy of its own source text as its complete output": http://www.nyx.net/~gthompso/quine.htm) in R? (The [quine] tag pulls up lots of examples in Python, Java, ... but apparently none in R.)

f <- function() { body() }

即将结束:

> f()
{
    body()
}

但缺少函数的名称.

最短的可能性怎么样?最容易混淆?

How about the shortest possibility? Most obfuscated?

编辑:从下面的各种答案中，似乎有多种方法可以定义自我指称和必须发生的环境:

edit: from the variety of answers below, it seems that there are a variety of ways to define self-referentiality and the environment in which it must occur:

• 在R环境中:函数->函数(@ bill_080)
• 在OS/shell环境中:程序->程序[或多或少等同于程序->文本]:(@kohske)
• other:函数->文本(@ JoshUlrich，@ James，问题如上定义)

• within the R environment: function -> function (@bill_080)
• within the OS/shell environment: program -> program [more or less equivalent to program -> text]: (@kohske)
• other: function -> text (@JoshUlrich, @James, problem as defined above)

注意:

• @Spacedman指出的R-help的线程(似乎强调简短而不是混淆)表明identical(quine,quine())是一个很好的测试用例，尽管它很棘手，因为环境会随身携带:identical(quine,quine(),ignore.environment=TRUE)可能会更容易.
• 最近(2015年10月)博客帖子提供了另一个答案...

• The thread from R-help pointed out by @Spacedman (which seems to emphasize obfuscation over brevity) suggests that identical(quine,quine()) is a good test case, although it's tricky because environments get carried along: identical(quine,quine(),ignore.environment=TRUE) might be easier.
• A recent (Oct 2015) blog post provides another answer ...

推荐答案

这是我能想到的最短的方法:

This is the shortest I can come up with:

> "f" <- function() call("<-", "f", f)
> f()
"f" <- function () 
call("<-", "f", f)

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