CS 541 Lecture -*- Outline -*-

* Naming (Schmidt 7.1)
	advert: naming essential to abstraction
		these techniques and concepts thus fundamental to seamntics

** Basic needs
***	primitive set of names, way to combine them
		e.g., g(f(x))
***	abstraction: abbreviation of long names
		e.g., lambda calculus without names
		e.g., in FL, have proc, bind and rec

** Environment: Identifier -> (Denotable-value + Unbound)
		(maps to Expressible-value in FL)

***	gives meaning to identifiers
			e.g., X := 2
		may be many environment values during program evaluation
			e.g., recursion, nesting

***	relationship between denotable and expressible values
			no reason that entities denotable by names
				should be same as
				entities computed by expressions
		let Denotable-value be entities denotable by names
		
		possible relationships between expressible and denotable values
		1. equality
		2. denotable contains expressible
			e.g., in language without first-class procedures
		3. denotable subset of expressible
			e.g., cannot bind a name to an error or \bot
		4. complex

***	Changes to FL semantics (for this discussion)
		p in Procedure = Denotable-value -> Expressible-value
		u in Environment = Identifier -> (Denotable-value + Unbound)
			(another tack would be to let Unbound be summand of DV)