Clean lists

Recursively remove NULL and zero-length elements from a list.

Usage

list_clean(x)

Arguments

x

(list)
A list to clean. If x is not a list, it is returned unchanged.

Value

If inherits(x, "list") is FALSE (for example, a data.frame, an atomic vector, NULL, or any S3 object whose class vector does not contain "list"), x is returned unchanged. Otherwise, a list is returned with NULL, zero-length, and recursively-empty elements removed at every level of nesting.

Examples

#----------------------------------------------------------------------------
# list_clean() examples
#----------------------------------------------------------------------------
library(bkbase)

# Removes NULL and zero-length elements, preserves names
x <- list(a = 1, b = NULL, c = logical(0L), d = 2)
list_clean(x)
#> $a
#> [1] 1
#> 
#> $d
#> [1] 2
#> 

# Recursive cleaning, including fully-empty sublists
y <- list(a = list(1, NULL), b = list(NULL, logical(0L)))
list_clean(y)
#> $a
#> $a[[1]]
#> [1] 1
#> 
#> 

# Non-list inputs are returned unchanged
list_clean(data.frame(x = 1:3))
#>   x
#> 1 1
#> 2 2
#> 3 3
list_clean(1:5)
#> [1] 1 2 3 4 5
list_clean(NULL)
#> NULL