Insert Elements at a Position — insert

Inserts values before the current element at index.

Usage

insert_at(x, index, values)

Arguments

x: A flexseq.
index: One-based insertion position in [1, length(x) + 1].
values: Values to insert.

Value

Updated sequence with inserted values.

Details

values is interpreted as a collection of elements to splice in.

Common cases:

Atomic vector (c("x", "y")): inserts one element per vector entry.
List (list("x", "y")): inserts one element per list entry.
flexseq: inserts all of its elements.
Empty input (list() or flexseq()): no change.

To insert one composite object (for example, a vector or a list) as a single element, wrap it in list(...).

This operation is persistent: x is not modified.

Examples

x <- flexseq("a", "b", "c", "d")
insert_at(x, 3, c("x", "y"))
#> Unnamed flexseq with 6 elements.
#> 
#> Elements:
#> 
#> [[1]]
#> [1] "a"
#> 
#> [[2]]
#> [1] "b"
#> 
#> ... (skipping 2 elements)
#> 
#> [[5]]
#> [1] "c"
#> 
#> [[6]]
#> [1] "d"
#> 
insert_at(x, 1, "start")
#> Unnamed flexseq with 5 elements.
#> 
#> Elements:
#> 
#> [[1]]
#> [1] "start"
#> 
#> [[2]]
#> [1] "a"
#> 
#> ... (skipping 1 element)
#> 
#> [[4]]
#> [1] "c"
#> 
#> [[5]]
#> [1] "d"
#> 
insert_at(x, length(x) + 1, "end")
#> Unnamed flexseq with 5 elements.
#> 
#> Elements:
#> 
#> [[1]]
#> [1] "a"
#> 
#> [[2]]
#> [1] "b"
#> 
#> ... (skipping 1 element)
#> 
#> [[4]]
#> [1] "d"
#> 
#> [[5]]
#> [1] "end"
#> 

# Insert one vector as a single element
insert_at(x, 3, list(c("u", "v")))
#> Unnamed flexseq with 5 elements.
#> 
#> Elements:
#> 
#> [[1]]
#> [1] "a"
#> 
#> [[2]]
#> [1] "b"
#> 
#> ... (skipping 1 element)
#> 
#> [[4]]
#> [1] "c"
#> 
#> [[5]]
#> [1] "d"
#>