CS 541 Lecture -*- Outline -*-

* design using grammars

	back and forth between examples and grammar

	grammar gives generality and elegance
	examples used to judge aesthetics

** FORTRAN IV identifiers

	a sequence of at most 6 alphanumeric characters,
	starting with an alphabetic character

	Try writing a regular expression or regular grammar for that

** if statements

	stmt ::= var := exp
		| if exp then stmt else exp
		| if exp then stmt

	this is ambiguous
		if b
		then if b2
		     then x := 3
		   else x := 4

	How to eliminate the ambiguity?
		require blocks always
		ending for else (fi)
		eliminate the lack of else (add a skip stmt)

** syntax of ML
	break the class into groups, have each group scan a chapter (2-7)
	for syntax of ML,
		write down page numbers
		write down a grammar for what you find

** ADTs for Pascal
	design syntax (as in CLU)
	for an abstract data type mechanism in Pascal
		start with a Stack example.
	
** add exception handling to C
	want to be able to raise exceptions
	have handler attached to any statement
	exceptions become part of the type of a procedure