obj_is_list: List checks

In vctrs: Vector Helpers

List checks

Description

• obj_is_list() tests if x is considered a list in the vctrs sense. It returns TRUE if:

  • x is a bare list with no class.

  • x is a list explicitly inheriting from "list".

• list_all_vectors() takes a list and returns TRUE if all elements of that list are vectors.

• list_all_size() takes a list and returns TRUE if all elements of that list have the same size.

• obj_check_list(), list_check_all_vectors(), and list_check_all_size() use the above functions, but throw a standardized and informative error if they return FALSE.

Usage

obj_is_list(x)

obj_check_list(x, ..., arg = caller_arg(x), call = caller_env())

list_all_vectors(x)

list_check_all_vectors(x, ..., arg = caller_arg(x), call = caller_env())

list_all_size(x, size)

list_check_all_size(x, size, ..., arg = caller_arg(x), call = caller_env())

Arguments

x	For ⁠vec_*()⁠ functions, an object. For ⁠list_*()⁠ functions, a list.
...	These dots are for future extensions and must be empty.
arg	An argument name as a string. This argument will be mentioned in error messages as the input that is at the origin of a problem.
call	The execution environment of a currently running function, e.g. caller_env(). The function will be mentioned in error messages as the source of the error. See the call argument of abort() for more information.
size	The size to check each element for.

Details

Notably, data frames and S3 record style classes like POSIXlt are not considered lists.

See Also

list_sizes()

Examples

obj_is_list(list())
obj_is_list(list_of(1))
obj_is_list(data.frame())

list_all_vectors(list(1, mtcars))
list_all_vectors(list(1, environment()))

list_all_size(list(1:2, 2:3), 2)
list_all_size(list(1:2, 2:4), 2)

# `list_`-prefixed functions assume a list:
try(list_all_vectors(environment()))

vctrs documentation built on Oct. 13, 2023, 1:05 a.m.