A scdrake's list with overloaded, strict access operators.

It behaves like a normal list, but, by default, it has more strict rules for non-existing elements: $, [, and [[ operators are overloaded for this class. They try to extract element(s) from a scdrake_list object, but throw an error when the element(s) does not exist. This behaviour can be avoided for [ and [[ by using the check = FALSE parameter, e.g. l[name, check = FALSE]. Also, in that case and for [, a scdrake_list with non-existing names and NULL values is returned instead of putting NA_character_ for them, which is the default behaviour for a base list, e.g.

> list(a = 2)["b"]
$<NA>
NULL

compared to

> scdrake_list(list(a = 2))["b", check = FALSE]
$b
NULL

attr(,"class")
[1] "scdrake_list"

However, this does not work for numeric subscripts.

Usage

scdrake_list(l = NULL)

# S3 method for scdrake_list
$(x, i)

# S3 method for scdrake_list
[(x, i, check = TRUE)

# S3 method for scdrake_list
[[(x, i, check = TRUE)

Arguments

l

A list.

x

An object of class scdrake_list.

i

A character scalar or vector: name / names of element(s) to extract.

check

A logical scalar: if TRUE, throw an error when non-existing names or subscripts are present.

Value

An object of class scdrake_list.

Examples

cfg <- scdrake_list(list(var_1 = 1, var_2 = 2))
# The standard list behavior.
cfg$var_1
#> [1] 1
cfg[["var_2"]]
#> [1] 2
cfg["var_1"]
#> $var_1
#> [1] 1
#> 
#> attr(,"class")
#> [1] "scdrake_list" "list"        
cfg[c("var_1", "var_2")]
#> $var_1
#> [1] 1
#> 
#> $var_2
#> [1] 2
#> 
#> attr(,"class")
#> [1] "scdrake_list" "list"        
if (FALSE) {
# Strict rules for non-existing elements - throws an error.
cfg$var_3
cfg[["var_3"]]
cfg[c("var_1", "var_3")]
}