add

Adds an element into a list if it doesn’t already exist (set-insertion).

add(xs:list, x:any) -> list

Description

The add function returns the list xs with x added at the end, but only if x is not already present in the list. This performs a set-insertion operation, ensuring no duplicate values in the resulting list.

`xs: list`

The list to add to.

`x: any`

An element to add to the list. If this is of a type incompatible with the list, it will be considered as null.

Examples

Add a new element to a list

from {xs: [1, 2, 3]}
xs = xs.add(4)

{xs: [1, 2, 3, 4]}

Try to add an existing element

from {xs: [1, 2, 3]}
xs = xs.add(2)

{xs: [1, 2, 3]}

Add to an empty list

from {xs: []}
xs = xs.add("hello")

{xs: ["hello"]}

add