Lesson Plan - 6.001 SP04 - recitation 17

object system exploration

more complicated example of specialization
has-a relationship?

sketching environment diagrams
- seat-of-the-pants (non-rule-based.. dangerous!)
- sketch is an inaccurate but along-the-right-lines version
  of the real thing
- env diagram is made up of frames and double-bubbles
  thought: only pay attention to rules that build those
- assuming working code, every variable in the code must be accessible
  (via the name rule) when it is used.  Variables are bound textually
  inside the expression (lambda, let, ...) that binds them.
- conclusion: frames must nest in order of the code that creates them

- sketch handlers
- sketch instance
- glue together
- trace one ask

mixed-up parents (use make- every time instead of saving a -part)

specialization

solutions:

1-7 too graphical to do here

8. location doesn't change! 
   object reports it's location to be the old place, but old contents
   doesn't contain object and new location's contents does.

9. location doesn't change!
   installation screwed up
   old location contents contains references to a mysterious
     mobile-thing with the same name as the foo-object
   new location contents contains a reference to a mysterious
     mobile-thing with the same name as the foo-object
   total count: 3 MOs in old, 2 MOs in new
   (MO's INSTALL, EMIT in FOO's INSTALL, get-method for LOCATION, 
    get-method&change-loc, get-method for LOCATION)

10. Tunes emit from the radio: I am the very model of a software engineer

11. Tunes blare from the boombox: I am the very model of a software engineer