Build a list

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.

lst(...)

Arguments

...	<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. An existing .data pronoun, provided e.g. inside dplyr::mutate(), is not available.

Value

A named list.

Life cycle

The lst() function is in the questioning stage. It is essentially rlang::list2(), but with a couple features copied from tibble(). It's not clear that a function for creating lists belongs in the tibble package. Consider using rlang::list2() instead.

Examples

# the value of n can be used immediately in the definition of x
lst(n = 5, x = runif(n))
#> $n
#> [1] 5
#> 
#> $x
#> [1] 0.8056800 0.8140513 0.4039110 0.2184310 0.4183614
#> 

# 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] 0.6688707 0.5076503 0.6603593
#> 

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
#>