50.2 Special operator

50.2.1 Inner function

A = matrix(1:9, nrow = 3)
Tr(A)

## Error in Tr(A): could not find function "Tr"

identical(stats:::Tr(A), sum(diag(A))) 

## [1] TRUE

50.2.2 Super assignment <<-

50.2.3 null default operator

https://rlang.r-lib.org/reference/op-null-default.html

寫 package 或工具函數時，想要讓預設值簡潔易讀

library(rlang)

## Warning: package 'rlang' was built under R version 4.3.3

NULL %||% 5

## [1] 5

"a" %||% 5

## [1] "a"

# help(`%||%`)
# `%||%` <- function(x, y) if (is.null(x)) y else x