lst() constructs a list, similar to base::list(), but with some of the
same features as tibble(). lst() builds components sequentially. When
defining a component, you can refer to components created earlier in the
call. lst() also generates missing names automatically.
See rlang::list2() for a simpler and faster alternative without tibble's
evaluation and auto-name semantics.
lst(...)<dynamic-dots>
A set of name-value pairs. These arguments are
processed with rlang::quos() and support unquote via !! and
unquote-splice via !!!. Use := to create columns that start with a dot.
Arguments are evaluated sequentially.
You can refer to previously created elements directly or using the .data
pronoun.
To refer explicitly to objects in the calling environment, use !! or
.env, e.g. !!.data or .env$.data for the special case of an object
named .data.
A named list.
# the value of n can be used immediately in the definition of x
lst(n = 5, x = runif(n))
#> $n
#> [1] 5
#>
#> $x
#> [1] 0.2220037 0.1208247 0.5305426 0.7951219 0.3532806
#>
# missing names are constructed from user's input
lst(1:3, z = letters[4:6], runif(3))
#> $`1:3`
#> [1] 1 2 3
#>
#> $z
#> [1] "d" "e" "f"
#>
#> $`runif(3)`
#> [1] 0.9371862 0.6326068 0.6565604
#>
a <- 1:3
b <- letters[4:6]
lst(a, b)
#> $a
#> [1] 1 2 3
#>
#> $b
#> [1] "d" "e" "f"
#>
# pre-formed quoted expressions can be used with lst() and then
# unquoted (with !!) or unquoted and spliced (with !!!)
n1 <- 2
n2 <- 3
n_stuff <- quote(n1 + n2)
x_stuff <- quote(seq_len(n))
lst(!!!list(n = n_stuff, x = x_stuff))
#> $n
#> [1] 5
#>
#> $x
#> [1] 1 2 3 4 5
#>
lst(n = !!n_stuff, x = !!x_stuff)
#> $n
#> [1] 5
#>
#> $x
#> [1] 1 2 3 4 5
#>
lst(n = 4, x = !!x_stuff)
#> $n
#> [1] 4
#>
#> $x
#> [1] 1 2 3 4
#>
lst(!!!list(n = 2, x = x_stuff))
#> $n
#> [1] 2
#>
#> $x
#> [1] 1 2
#>