The atomic vector constructors are equivalent to
c() but allow
you to be more explicit about the output type. Implicit coercions
(e.g. from integer to logical) follow the rules described in
vector-coercion. In addition, all constructors support splicing:
if you supply bare lists or explicitly
spliced lists, their contents are spliced into the
output vectors (see below for details).
ll() is a list
constructor similar to
base::list() but with splicing semantics.
lgl(...) int(...) dbl(...) cpl(...) chr(..., .encoding = NULL) bytes(...) ll(...)
Components of the new vector. Bare lists and explicitly spliced lists are spliced.
If non-null, passed to
Splicing is an operation similar to flattening one level of nested
lists, e.g. with
base::unlist(x, recursive =
ll() returns its arguments as a
list, just like
list() would, but inner lists qualifying for
splicing are flattened. That is, their contents are embedded in the
surrounding list. Similarly,
chr() concatenates its arguments and
returns them as a single character vector, but inner lists are
flattened before concatenation.
Whether an inner list qualifies for splicing is determined by the
type of splicing semantics. All the atomic constructors like
chr() have list splicing semantics: bare lists
and explicitly spliced lists are spliced.
There are two list constructors with different splicing
ll() only splices lists explicitly marked with
# These constructors are like a typed version of c(): c(TRUE, FALSE)#>  TRUE FALSElgl(TRUE, FALSE)#>  TRUE FALSE# They follow a restricted set of coercion rules: int(TRUE, FALSE, 20)#>  1 0 20# Lists can be spliced: dbl(10, list(1, 2L), TRUE)#>  10 1 2 1# They splice names a bit differently than c(). The latter # automatically composes inner and outer names: c(a = c(A = 10), b = c(B = 20, C = 30))#> a.A b.B b.C #> 10 20 30# On the other hand, rlang's ctors use the inner names and issue a # warning to inform the user that the outer names are ignored: dbl(a = c(A = 10), b = c(B = 20, C = 30))#> Warning: Outer names are only allowed for unnamed scalar atomic inputs#> A B C #> 10 20 30dbl(a = c(1, 2))#> Warning: Outer names are only allowed for unnamed scalar atomic inputs#>  1 2# As an exception, it is allowed to provide an outer name when the # inner vector is an unnamed scalar atomic: dbl(a = 1)#> a #> 1# Spliced lists behave the same way: dbl(list(a = 1))#> a #> 1dbl(list(a = c(A = 1)))#> Warning: Outer names are only allowed for unnamed scalar atomic inputs#> A #> 1# bytes() accepts integerish inputs bytes(1:10)#>  01 02 03 04 05 06 07 08 09 0abytes(0x01, 0xff, c(0x03, 0x05), list(10, 20, 30L))#>  01 ff 03 05 0a 14 1e# The list constructor has explicit splicing semantics: ll(1, list(2))#> [] #>  1 #> #> [] #> [][] #>  2 #> #># Note that explicitly spliced lists are always spliced: ll(!!! list(1, 2))#> [] #>  1 #> #> [] #>  2 #>