insert
Inserts a new element into a linear container.
Syntax

insert(X, i, x)

X
is a linear container 
i
is an integer 
x
is any compatible object

Description
If X
is a linear container, i
a valid index in a container of size #X + 1
, and x
a value that can be present in X
, then insert(X, i, x)
returns X
with the value x
inserted at index i
(so that i
is the index of x
in insert(X, i, x)
).
Examples
"Hello world"
Hello world
insert(ans, 6, ",")
Hello, world
insert(ans, −1, "!")
Hello, world!