R 中的从右到左运算符结合性是否可能? [英] Is right-to-left operator associativity in R possible?

问题描述

我是 R 新手，我刚刚发现我患有支架恐惧症(请参阅关联).我喜欢 magrittr 符号 %>% 的工作方式，因为它在某些情况下避免了嵌套括号，并使代码更具可读性.我来自 Mathematica，那里有一个非常相似的原生 // 符号来做 %>% 所做的事情.下面是一些 R 和 Mathematica 的比较:

I'm new to R, and I just discovered I suffer from Bracket Phobia (see comment in the link). I like the way magrittr notation %>% works, because it avoids nested parenthesis in some situations, and makes code more readable. I came from Mathematica, where there is a very similar native // notation to do what %>% does. Here are some R and Mathematica comparisons:

#R Notation    
c(1.5,-2.3,3.4) %>% round %>% abs %>% sum  

#Mathematica Notation
{1.5,-2.3,3.4}//Round//Abs//Total

到目前为止一切顺利，但是，我的问题是:

So far so good, but, my question is:

有什么方法可以模仿 Mathematica @ 符号，R 中的从右到左结合性?

Is there some way to mimic Mathematica @ notation, with right-to-left associativity in R?

这是它在 Mathematica 中的工作原理，用于解决上面相同的代码:

Here is how it works in Mathematica, to solve the same code above:

Total@Abs@Round@{1.5,-2.3,3.4}

在 Mathematica 中也可以写成:

In Mathematica it can also be write as:

Total[Abs[Round[{1.5,-2.3,3.4}]]]

就像在 R 中一样:

sum(abs(round(c(1.5,-2.3,3.4))))

但是在 R 中有这样的东西会更干净(也很酷):

But it would be much more clean (and cool) to have in R something like this:

sum@abs@round@c(1.5,-2.3,3.4)

PS:我知道 @ 在 S4 类中使用，这不是一个好主意.这只是一个说明性的比较.

PS: I know @ is used in S4 classes, and is not a good idea. This is just an illustrative comparison.

推荐答案

backpipe 包就是为此目的而设计和创建的.它为 ma​​grittr、pipeR 和任何前向管道操作符提供了一个 backpipe(从右到左)操作符.backpipe 可以在 github 和 CRAN.

The backpipe package was designed and created for this purpose. It provides a backpipe (right-to-left) operator for magrittr, pipeR and generally for any forward pipe operator. backpipe can be found on github and on CRAN.

library(magrittr)  # or library(pipeR)
library(backpipe)

x <- c(1.5,-2.3,3.4)
sum %<% abs %<% round %<% x

all.equal(                             # TRUE
      x %>% round %>% abs %>% sum,
      sum %<% abs %<% round %<% x
)

backpipe 也不受其他参数的限制，就像@BenBolker 的解决方案一样.例如，这适用于 backpipe :

backpipe also is not limited by additional parameters as is the case of the @BenBolker's solution. This, for example, works with backpipe :

mean(na.rm=TRUE) %<% c(1:3,NA)  

另请参阅有关讨论此问题的 magrittr github 问题 的讨论.

See also the discussion on the magrittr github issue that discuss this.

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