list_of S3 class for homogenous lists

A list_of object is a list where each element has the same type. Modifying the list with $, [, and [[ preserves the constraint by coercing all input items.

Usage

list_of(..., .ptype = NULL)

as_list_of(x, ...)

is_list_of(x)

# S3 method for vctrs_list_of
vec_ptype2(x, y, ..., x_arg = "", y_arg = "")

# S3 method for vctrs_list_of
vec_cast(x, to, ...)

Arguments

...

Vectors to coerce.

.ptype

If NULL, the default, the output type is determined by computing the common type across all elements of ....

Alternatively, you can supply .ptype to give the output known type. If getOption("vctrs.no_guessing") is TRUE you must supply this value: this is a convenient way to make production code demand fixed types.

x

For as_list_of(), a vector to be coerced to list_of.

y, to

Arguments to vec_ptype2() and vec_cast().

x_arg, y_arg

Argument names for x and y. These are used in error messages to inform the user about the locations of incompatible types (see stop_incompatible_type()).

Details

Unlike regular lists, setting a list element to NULL using [[ does not remove it.

Examples

x <- list_of(1:3, 5:6, 10:15)
if (requireNamespace("tibble", quietly = TRUE)) {
  tibble::tibble(x = x)
}
#> # A tibble: 3 × 1
#>             x
#>   <list<int>>
#> 1         [3]
#> 2         [2]
#> 3         [6]

vec_c(list_of(1, 2), list_of(FALSE, TRUE))
#> <list_of<double>[4]>
#> [[1]]
#> [1] 1
#> 
#> [[2]]
#> [1] 2
#> 
#> [[3]]
#> [1] 0
#> 
#> [[4]]
#> [1] 1
#>