class notes for Feb. 17 taken by Yi-Fan Chien	


1) we went over some of the materials needed for project2:

      CAHRLIT = '(NOT('|\|Unprintable)|\'|\n|\t|\\)'
   
	So 'ABCD' would yield an error.

	BADCHAR1 = "|'(unprintable)'|'"|'\'
	BADCHAR2 = '(NOT('|EOL))(NOT('|EOL))+
	BADCHAR3 = '(NOT(')* EOL)

2) INTRODUCED CONCEPT OF LOOK AHEAD
	      
	      #OF CHARS NEEDED TO LOCATE END OF TOKEN

EXAMPLE1:
		123 + 456      -> 1 CHAR LOOK AHEAD (NEED BUFFERING)

EXAMPLE2: 
		1.20           -> NEED MORE THAN 1 BUFFER

CASE:

	1/*P
	 /X ........OTHER COMMENTS  */





         /                 *          *          /  
->STATE1---->FINAL_STATE2---->STATE3---->STATE4---->FINAL_STATE5  
   |                          |   ^
   |                          |   |
   ---->FINAL_STATE           -----
		              NOT(*|/)



CASE: FORTRAN ; SPACE IS IGNORED

space not ignored  ->      Do  10  I = 1 . 100  => 7 tokens

                                    |   |
                                    |   |
space ignored      ->      Do  10  I| = | 1 . 100  => 3 tokens 
                                    |   |
                              1     | 2 |     3 token 

##########################################################################


 SCANNER DEF.              ------------
                    ------>|JLEX | LEX|-----> Complete Scanner Class
 REG. EXPR. + CODE         ------------


Question:  How to translate Reg. Expr. to F.A ?
                 
                   A            B             C
	   state1------>state2------>state3------>final-state4


        use transition table

	   A  B  C
        1  2
        2     3
        3        4
        4
 
	Step 1) Reg. Expr. -----> Non-Deterministic Finite Automaton (NFA)

	     2) NFA ------->Deterministic Finite Automaton (DFA)

	     3) Optimize DFA

***********************************************************************

	NFA allows:


                    a
	    State1----->state2
             |  |  a
             |  ------->state3  
             |
             |   a
             ---------->state4

       
        DFA allows:

	             a 
	    State1------->state1 and state2 and state3