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 1
If 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.