CS 342 Lecture -*- Outline -*-

* the Smalltalk interpreter

** differences from CLU (page 292)
	values are tagged with their class
		see STVALUEREC owner field on page 293,
		vs. CLUVALUEREC on page 222
	symbols
	representation (instance variable list in clrep under CLASSREC p. 293)
		has to deal with inheritance
	application of functions
		looks in global function environment after class hierarchy
	special treatment of new
		setting self (inherited from object as an instance variable)
	must build top-level environment with true, false, and Object

** details
	DRAW PICTURES

*** data structures (p. 293)
	objects have:
		owner (class)
		vtype (kind of value)
		userval (environment giving fields, including self)
	ints and symbols have Object as their class, but special vtype.

	look at the 3 kinds of records on page 293, give examples with sets
		or stacks.
	start from the classes variable and show what the system looks like

*** evaluation (p. 295)
	evaluation takes a recieving object as 3rd argument
		(was cluster in CLU)

	variables: look first for formals, then instance variables,
			then globals

	evaluation of applications (code on page 296)
		control operations can't be redefined
		value-ops can be defined as messages
		global functions last case, unless 0 arguments

	what does method lookup do (p. 296)?

	newop makes self point to the object

*** initialization (page 297)
	How to define Object as a class?
		can't so it must be built-in.