arrays should have ability to push() and pop()

[jessfraz]

No description provided.

[Irev-Dev]

imo.

❌

const myArr = [1,2,3]
myArr.push(4)
log(myArr) // [1,2,3,4]

✅

const myArr = [1,2,3]
const myOtherArr = push(myArr, 4)
log(myArr) // [1,2,3]

We don't want to allow mutation, opens too much of a can of worms, we'll loose our ability to introspect program memory.

[jtran]

push() was merged in #4341.