lazy_dots: Capture ... (dots) for later lazy evaluation.

In lazyeval: Lazy (Non-Standard) Evaluation

Description

Capture ... (dots) for later lazy evaluation.

Usage

lazy_dots(..., .follow_symbols = FALSE, .ignore_empty = FALSE)

Arguments

...	Dots from another function
.follow_symbols	If TRUE, the default, follows promises across function calls. See vignette("chained-promises") for details.
.ignore_empty	If TRUE, empty arguments will be ignored.

Value

A named list of lazy expressions.

Examples

lazy_dots(x = 1)
lazy_dots(a, b, c * 4)

f <- function(x = a + b, ...) {
  lazy_dots(x = x, y = a + b, ...)
}
f(z = a + b)
f(z = a + b, .follow_symbols = TRUE)

# .follow_symbols is off by default because it causes problems
# with lazy loaded objects
lazy_dots(letters)
lazy_dots(letters, .follow_symbols = TRUE)

# You can also modify a dots like a list. Anything on the RHS will
# be coerced to a lazy.
l <- lazy_dots(x = 1)
l$y <- quote(f)
l[c("y", "x")]
l["z"] <- list(~g)

c(lazy_dots(x = 1), lazy_dots(f))

Example output

$x
<lazy>
  expr: 1
  env:  <environment: R_GlobalEnv>

attr(,"class")
[1] "lazy_dots"
[[1]]
<lazy>
  expr: a
  env:  <environment: R_GlobalEnv>

[[2]]
<lazy>
  expr: b
  env:  <environment: R_GlobalEnv>

[[3]]
<lazy>
  expr: c * 4
  env:  <environment: R_GlobalEnv>

attr(,"class")
[1] "lazy_dots"
$x
<lazy>
  expr: x
  env:  <environment: 0x2793e88>

$y
<lazy>
  expr: a + b
  env:  <environment: 0x2793e88>

$z
<lazy>
  expr: a + b
  env:  <environment: R_GlobalEnv>

attr(,"class")
[1] "lazy_dots"
$x
<lazy>
  expr: a + b
  env:  <environment: 0x27adbe0>

$y
<lazy>
  expr: a + b
  env:  <environment: 0x27adbe0>

$z
<lazy>
  expr: a + b
  env:  <environment: R_GlobalEnv>

attr(,"class")
[1] "lazy_dots"
[[1]]
<lazy>
  expr: letters
  env:  <environment: R_GlobalEnv>

attr(,"class")
[1] "lazy_dots"
[[1]]
<lazy>
  expr: letters
  env:  <environment: R_GlobalEnv>

attr(,"class")
[1] "lazy_dots"
$y
<lazy>
  expr: f
  env:  <environment: R_GlobalEnv>

$x
<lazy>
  expr: 1
  env:  <environment: R_GlobalEnv>

attr(,"class")
[1] "lazy_dots"
$x
<lazy>
  expr: 1
  env:  <environment: R_GlobalEnv>

[[2]]
<lazy>
  expr: f
  env:  <environment: R_GlobalEnv>

attr(,"class")
[1] "lazy_dots"

lazyeval documentation built on May 2, 2019, 2:11 a.m.