DOC : Add compile state example (#2910)

docs/src/usage/compile.rst

@@ -257,7 +257,26 @@ constants. For example:
 
 In order to have the change of state reflected in the outputs of ``fun`` you
 again have two options. The first option is to simply pass ``state`` as input
-to the function. In some cases this can be pretty inconvenient. Hence,
+to the function.
+
+.. code-block:: python
+
+  state = [mx.array(1.0)]
+
+  @mx.compile
+  def fun(x, state):
+      return x + state[0]
+
+  # Prints array(2, dtype=float32)
+  print(fun(mx.array(1.0), state))
+
+  # Update state
+  state[0] = mx.array(5.0)
+
+  # Prints array(6, dtype=float32)
+  print(fun(mx.array(1.0), state))
+
+In some cases this can be pretty inconvenient. Hence,
 :func:`compile` also has a parameter to capture implicit inputs:
 
 .. code-block:: python