Create a List With Unique Named Keys

Create a list with unique names/keys, erroring if any duplicate names/keys are found.

Usage

knlist(...)

is.knlist(x)

as.knlist(x, ...)

# Default S3 method
as.knlist(x, ..., .recursive = FALSE)

# S3 method for class 'knlist'
names(x) <- value

# S3 method for class 'knlist'
c(...)

Arguments

...: for knlist: named objects, for as.knlist: passed to other methods.
x: object to be coerced or tested.
.recursive: boolean indicating whether to recursively validate nested lists. If TRUE then all nested lists will be validated and converted to knlists, if FALSE then only the top level list will be validated and converted to a knlist.
value: a character vector the same length as x. Resulting names must be unique.

Value

A list of class knlist. For is.knlist() a boolean.

Details

names<- method for knlist objects will apply the names and then validate that the resulting names are unique.

c.knlist method will combine the objects and then validate that the resulting knlist's names are unique.

For a list with unique keys of names and indexes, see klist.

Note

knlists compare names using C's strcmp function.

Examples

x <- knlist(a = 1, b = 2, c = 3)
try(knlist(b = 1, a = 2, a = 1)) # duplicate keys not allowed
#> Error in knlist(b = 1, a = 2, a = 1) : Names must be unique.
#> Duplicate name: a
try(x[[1]] <- 1) # knlist only accepts character indexing for assignment
#> Error : Only character indexing is allowed for assignment into knlist objects

# objects within a knlist are not subject to validation
knlist(x = 1, list(a = 1, a = 2))
#> Error in knlist(x = 1, list(a = 1, a = 2)): All elements must be named.
try(knlist(x = 1, knlist(a = 1, a = 2))) # but nested knlists are
#> Error in knlist(a = 1, a = 2) : Names must be unique.
#> Duplicate name: a

# recursively validate and convert to knlist
x <- list(a = 1, b = list(x = 1, y = 2))
x <- as.knlist(x, .recursive = TRUE)
class(x[[2]]) # nested list is now a knlist
#> [1] "knlist"

is.knlist(knlist(a = 1)) # TRUE
#> [1] TRUE

try(names(x) <- c("a", "a")) # names are validated when changed
#> Error in `names<-.knlist`(`*tmp*`, value = c("a", "a")) : 
#>   Names must be unique.
#> Duplicate name: a

# c() method for knlist objects also validates
try(c(knlist(a = 1), list(a = 3)))
#> Error in c.knlist(knlist(a = 1), list(a = 3)) : Names must be unique.
#> Duplicate name: a