Destructuring assignments in R with the . object.
library(dotty)
# extract number of rows, number of columns from mtcars
.[nr, nc] <- dim(mtcars)
c(nr, nc)## [1] 32 11# extract first, last element of vector
.[first, .., last] <- c(1, 2, 3, 4, 5)
c(first, last)## [1] 1 5# extract a value by name
.[beta = beta] <- list(alpha = 1, beta = 2, gamma = 3)
beta## [1] 2# unpack nested values
.[x, .[y, .[z]]] <- list(1, list(2, list(3)))
c(x, y, z)## [1] 1 2 3# split version components
.[major, minor, patch] <- getRversion()
c(major, minor, patch)## [1] 4 4 1If you’d like to use dotty in your CRAN package, you can
avoid R CMD check warnings by including a file called
R/zzz.R with the contents:
.onLoad <- function(libname, pkgname) {
dotty::dotify()
}This function patches codetools so
that variables usages in . expressions can be linted as
though those were regular bindings / assignments.