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## ----include = FALSE----------------------------------------------------------
knitr::opts_chunk$set(
collapse = TRUE,
comment = "#>"
)
## ----setup--------------------------------------------------------------------
library(withr)
## ----include = FALSE----------------------------------------------------------
op <- options()
## -----------------------------------------------------------------------------
sloppy <- function(x, sig_digits) {
options(digits = sig_digits)
print(x)
}
pi
sloppy(pi, 2)
pi
## ----include = FALSE----------------------------------------------------------
options(op)
## -----------------------------------------------------------------------------
neat <- function(x, sig_digits) {
op <- options(digits = sig_digits)
on.exit(options(op), add = TRUE)
print(x)
}
pi
neat(pi, 2)
pi
## -----------------------------------------------------------------------------
neater <- function(x, sig_digits) {
op <- options(digits = sig_digits)
defer(options(op))
print(x)
}
pi
neater(pi, 2)
pi
## -----------------------------------------------------------------------------
defer_stack <- function() {
cat("put on socks\n")
defer(cat("take off socks\n"))
cat("put on shoes\n")
defer(cat("take off shoes\n"))
}
defer_stack()
## -----------------------------------------------------------------------------
on_exit_last_one_wins <- function() {
cat("put on socks\n")
on.exit(cat("take off socks\n"))
cat("put on shoes\n")
on.exit(cat("take off shoes\n"))
}
on_exit_last_one_wins()
## ----eval = getRversion() >= "3.5.0"------------------------------------------
on_exit_stack <- function() {
cat("put on socks\n")
on.exit(cat("take off socks\n"), add = TRUE, after = FALSE)
cat("put on shoes\n")
on.exit(cat("take off shoes\n"), add = TRUE, after = FALSE)
}
on_exit_stack()
## -----------------------------------------------------------------------------
defer_queue <- function() {
cat("Adam gets in line for ice cream\n")
defer(cat("Adam gets ice cream\n"), priority = "last")
cat("Beth gets in line for ice cream\n")
defer(cat("Beth gets ice cream\n"), priority = "last")
}
defer_queue()
## -----------------------------------------------------------------------------
neater <- function(x, sig_digits) {
op <- options(digits = sig_digits) # record orig. "digits" & change "digits"
defer(options(op)) # schedule restoration of "digits"
print(x)
}
## -----------------------------------------------------------------------------
local_digits <- function(sig_digits, envir = parent.frame()) {
op <- options(digits = sig_digits)
defer(options(op), envir = envir)
}
## -----------------------------------------------------------------------------
neato <- function(x, digits) {
local_digits(digits)
print(x)
}
pi
neato(pi, 2)
neato(pi, 4)
## -----------------------------------------------------------------------------
neatful <- function(x) {
local_digits(1)
print(x)
local_digits(3)
print(x)
local_digits(5)
print(x)
}
neatful(pi)
## -----------------------------------------------------------------------------
neatest <- function(x, sig_digits) {
local_options(list(digits = sig_digits))
print(x)
}
pi
neatest(pi, 2)
neatest(pi, 4)
## ----eval = FALSE-------------------------------------------------------------
# neat_with <- function(x, sig_digits) {
# # imagine lots of code here
# withr::with_options(
# list(digits = sig_digits),
# print(x)
# )
# # ... and a lot more code here
# }
## ----eval = FALSE-------------------------------------------------------------
# neat_local <- function(x, sig_digits) {
# withr::local_options(list(digits = sig_digits))
# print(x)
# # imagine lots of code here
# }
## -----------------------------------------------------------------------------
library(withr)
defer(print("hi"))
pi
# this adds another deferred event, but does not re-message
local_digits(3)
pi
deferred_run()
pi
## ----eval = FALSE-------------------------------------------------------------
# defer(print("hi"))
# #> Setting global deferred event(s).
# #> i These will be run:
# #> * Automatically, when the R session ends.
# #> * On demand, if you call `withr::deferred_run()`.
# #> i Use `withr::deferred_clear()` to clear them without executing.
|
