[BUG]: no way to append to a list, returning a new list with the added value

[paultag]

Describe the bug

I would like to be able to append to a list -- something like:

fn x = (something) => {
    return something.append(1)
}

const y = x([3, 2])

Steps to Reproduce

n/a

Expected Behavior

n/a

Screenshots and Recordings

No response

Desktop OS

Debian

Browser

Chrome

Version

main

Additional Context

No response

[nrc]

What's your use case for this? I'm curious about the larger task you're doing that requires it

[jtran]

#4232 implements this by the most straight forward approach of cloning the Vec and pushing to it.

This technically works, but if anyone pushes inside a loop, it's O(n^2). Do we really want to introduce this? Seems like a big foot-gun.

As an alternative, I propose persistent data structures since they fit better with immutability. Clojure makes good use of hash array mapped tries to provide a persistent interface, while mutating internally for better performance.

[jtran]

Resolved by #4341.