| Title: | The Unpacking Dot Operator |
|---|---|
| Description: | Provides a `.` object which can be used for unpacking assignments. For example, `.[rows, columns] <- dim(cars)` could be used to pull the number of rows and number of columns from `dim(cars)` into individual variables `rows` and `columns` in a single step. |
| Authors: | Kevin Ushey [aut, cre] |
| Maintainer: | Kevin Ushey <[email protected]> |
| License: | MIT + file LICENSE |
| Version: | 0.1.0.9000 |
| Built: | 2025-02-18 19:15:54 UTC |
| Source: | https://github.com/kevinushey/dotty |
Use dotty to perform destructuring assignments.
Please see the examples below for usages.
..
An object of class dotty of length 0.
# extract number of rows, number of columns from mtcars .[nr, nc] <- dim(mtcars) c(nr, nc) # extract first, last element of vector .[first, .., last] <- c(1, 2, 3, 4, 5) c(first, last) # extract a value by name .[beta = beta] <- list(alpha = 1, beta = 2, gamma = 3) beta # unpack nested values .[x, .[y, .[z]]] <- list(1, list(2, list(3))) c(x, y, z) # split version components .[major, minor, patch] <- getRversion() c(major, minor, patch)# extract number of rows, number of columns from mtcars .[nr, nc] <- dim(mtcars) c(nr, nc) # extract first, last element of vector .[first, .., last] <- c(1, 2, 3, 4, 5) c(first, last) # extract a value by name .[beta = beta] <- list(alpha = 1, beta = 2, gamma = 3) beta # unpack nested values .[x, .[y, .[z]]] <- list(1, list(2, list(3))) c(x, y, z) # split version components .[major, minor, patch] <- getRversion() c(major, minor, patch)
destructure is primarily used to help define how an
object should be prepared, or transformed, prior to a
destructuring assignment. This can be relevant for
objects which have unique subsetting semantics – for
example, numeric_version objects.
destructure(object)destructure(object)
object |
An R object. |
Packages which would like to define special destructring semantics for certain object classes can implement methods for this class.
When using dotty within an R package, you might see NOTEs during
R CMD check of the form:
dotify()dotify()
N checking R code for possible problems (1.8s)
<package>: no visible binding for global variable <variable>
Undefined global functions or variables:
<variable>
This occurs because the codetools package, which is used for static
analysis of R code during R CMD check, does not recognize that e.g.
.[apple] <- 42 would create a variable called apple in the current
scope. Calling dotty::dotify() in your package's .onLoad() will
allow dotty to patch codetools in a way that will allow it to
understand dotty usages, and so prevent these R CMD check notes
from being emitted.