- `LH = addlistener (OBJ, EVENT, FCN)`
- `LH = addlistener (OBJ, PROP, POSTSET, FCN)`

Register listener function `FCN` for an event or property change on `OBJ`.

The returned listener handle may be used to control the lifetime of the
listener.

See also: `notify`, `events`, `properties`.

### References

- https://www.mathworks.com/help/matlab/ref/addlistener.html
- https://octave.sourceforge.io/octave/function/addlistener.html