insert_at: Insert Elements at a Position

In Immutables: Fast and Functional Data Structures

Insert Elements at a Position

Description

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.

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.

Value

Updated sequence with inserted values.

Examples

x <- flexseq("a", "b", "c", "d")
insert_at(x, 3, c("x", "y"))
insert_at(x, 1, "start")
insert_at(x, length(x) + 1, "end")

# Insert one vector as a single element
insert_at(x, 3, list(c("u", "v")))

Immutables documentation built on April 29, 2026, 1:06 a.m.