ellipsis
Tools for Working with ...
The ellipsis is a powerful tool for extending functions. Unfortunately this power comes at a cost: misspelled arguments will be silently ignored. The ellipsis package provides a collection of functions to catch problems and alert the user.
Adding ... to an S3 generic allows methods to take additional
arguments, but it comes with a big downside: any misspelled or extraneous
arguments will be silently ignored. This package explores an approach to
making ... safer, by supply a function that a generic can use to warn
if any elements of ... were not evaluated.
In the long run, this code is likely to live elsewhere (maybe R-core might be interested in making it part of base R). This repository tracks the current state of the experiment.
Thanks to Jenny Bryan for the idea, and Lionel Henry for the heart of the implementation.
Installation
devtools::install_github("hadley/ellipsis")
Example
safe_median() works like median() but warns if any elements of ...
are never evaluated
library(ellipsis)x <- c(1:10, NA)safe_median(x)#> [1] 5.5safe_median(x, TRUE)#> Warning: Some components of ... were not used: ..1#> [1] 5.5safe_median(x, na.rm = TRUE)#> [1] 5.5safe_median(x, na.mr = TRUE)#> Warning: Some components of ... were not used: na.mr#> [1] 5.5
News
ellipsis 0.1.0
-
New
check_dots_unnamed()that checks that all components of...are unnamed (#7). -
Fix a bug that caused
check_dots_used()to emit many false positives (#8)
ellipsis 0.0.2
- Fix a
PROTECTion error