[the__alchemist]

I challenge you to write the function signature I posted in Python, Javascript, or Kotlin; I'm confident you will not be able to, and the alternatives will be more provincial and unergonomic.

Hint: Python and Javascript will use the type passed to determine mutability. Kotlin will let you pass a mutableStateFlow etc that can be used for, e.g., top-level data structure, but not an arbitrary variable. (e.g. a data structure field, or free variable).

The most popular languages, outside of C and C++, cannot pass pointers. And, raw pointers are not ideal; they lose type safety, memory safety etc.

There are always canonical patterns for a given language to write a function like I did. I find them to be universally more complicated and less explicit/versatile than what I posted; they require code to permeate beyond the function signature.

[constantcrying]

It works the moment you wrap the int in a class.

class A:

    a = 0

def modify (v):

    v.a = 2

a1 = A()

a1.a = 1

print(a1.a)

modify(a1)

print(a1.a)