R中的二进制运算符/中缀函数是否通用?以及如何利用? [英] Are binary operators / infix functions in R generic? And how to make use of?

问题描述

来自 http://adv-r.had.co.nz/Functions. html 或

From http://adv-r.had.co.nz/Functions.html or R: What are operators like %in% called and how can I learn about them? I learned that it is possible to write own "binary operators" or "infix functioncs" using the %-sign. One example would be

'%+%' <- function(a, b) a*b
x <- 2
y <- 3
x %+% y # gives 6 

但是如果它们来自预定义的类，是否可以以通用的方式使用它们(因此在某些情况下，我不必使用%-符号)?例如，如果x + y来自类prod，则应给出6.

But is it possible to use them in a generic way if they are from a pre-defined class (so that in some cases I don't have to use the %-sign)? For exampple x + y shall give 6 if they are from the class prod.

推荐答案

是的，这是可能的:使用'+.<class name>' <- function().

Yes, this is possible: use '+.<class name>' <- function().

'+.product' <- function(a, b) a * b
'+.expo' <- function(a, b) a ^ b

m <- 2; class(m) <- "product"
n <- 3; class(n) <- "product"

r <- 2; class(r) <- "expo"
s <- 3; class(s) <- "expo"

m + n # gives 6
r + s # gives 8

安全说明

如果至少一个参数来自对应的类m + 4给您2 * 4 = 8而不是2 + 4 = 6，则将调用新定义的函数.如果类别不匹配，则会收到错误消息(例如r + m).因此，总而言之，请确保要在诸如+之类的基本功能之后建立一个新功能.

safety notes

The new defined functions will be called if at least one of the arguments is from the corresponding class m + 4 gives you 2 * 4 = 8 and not 2 + 4 = 6. If the classes don't match, you will get an error message (like for r + m). So all in all, be sure that you want to establish a new function behind such basic functions like +.

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