Check whether a path exists in a nested list

Check whether a path exists in a nested list

Usage

list_has(x, path)

Arguments

x

A nested list to traverse.

Lists are traversed recursively. Non-list objects are treated as leaves. Data frames are not traversed and are treated as leaf values.

path

Character or integer vector giving the path to retrieve.

For a character path, each component selects a named element at the current level. For an integer path, each component selects an element by position. Positional indices are one-based, following normal R indexing conventions.

The path is evaluated from left to right. For example, c("b", "y", "i") means x[["b"]][["y"]][["i"]].

Value

A logical scalar:

• TRUE if path exists in x;

• FALSE otherwise.

See also

Other lstrrr_core: list_delete(), list_depth(), list_get(), list_nleaf(), list_path(), list_set()

Examples

x <- list(
  a = 1,
  b = list(
    x = 1,
    y = list(i = 1, j = 2)
  ),
  unnamed = list(10, 20),
  df = data.frame(z = 1:3)
)

list_has(x, c("b", "x"))
#> [1] TRUE
list_has(x, c("b", "y", "i"))
#> [1] TRUE
list_has(x, c("b", "y", "k"))
#> [1] FALSE

# Integer paths use positional indices
list_has(x, c(2L, 2L, 1L))
#> [1] TRUE

# Empty path refers to `x` itself, always returns TRUE
list_has(x, character(0))
#> [1] TRUE

# Data frames are treated as leaves
list_has(x, "df")
#> [1] TRUE
list_has(x, c("df", "z")) # FALSE
#> [1] FALSE