Prototype mutable tensors + question: are they desirable?

[david-berthelot]

Currently we cannot do write part of a tensor using numpy syntax:

import jax.numpy as jn

v = jn.arange(10)
v[2:4] += 1  
# TypeError: '<class 'jax.interpreters.xla.DeviceArray'>' object does not support item assignment.
# JAX arrays are immutable; perhaps you want jax.ops.index_update or jax.ops.index_add instead?

However in numpy it works

import numpy as np

v = np.arange(10)
v[2:4] += 1  
print(v)
# [0 1 3 4 4 5 6 7 8 9]

I'm interested in prototyping feasibility but I also wonder if it's a desirable feature generally speaking. Feedback welcome.