CS 631, Fall 2009


Assignment #12: 10 points

Date Due: Monday, 12/14/09.


	Read Sections 6.3, 6.6.

(3)  1.	Exercise 6.2.2(ii).  Give: (a) syntax tree, (b) quadruples and 
	(c) triples.

(2)  2.	Translate the executable statements of the following C program
	into three-address code using the SDD for while statements in
	Figure 6.36:

		main() {
		    int i=0, a[10];
		    while (i<10) {
		        a[i]=0; i=i+1;
  		    }   
		}

(2)  3. Exercise 6.6.1(b).

(3)  4. Modify your lex/yacc expression compiler from HW#11, Problem 4, 
	to extend the translation scheme of Figure 6.20, (based on C version
	in Figure 8.15 of Aho, 1st ed.) to include multiplication (*), division
	(/), subtraction (-) and integer constants.   Add a grammar rule:

		E -> NUM 

	which assigns a constant to a temporary variable generated by the 
	newtemp() function.  This can be done by having lex recognize the
	NUM token and using sscanf(yytext,"%d",&yylval) to return the numeric 
	value of NUM in yylval to yacc.  The translation of the grammar rule
	will assign the constant to the temporary variable in the form:

		$$nn = NUM.yylval;

	The value of the constant will be stored as $1 on the yacc value
	stack and needs to be printed as a string of digits in the assign.
	Use printf("%d",$1) to accomplish this.  Test your expression compiler
	on:
		x = -b+4*a*c/(2*a);

	As in HW11, Problem 4, print the symbol table entries after the code.
	Hand in your lex/yacc program and the output from your compiler on the
	test expression.** 


      **For full credit, turn in well commented program listing and
	output from your computer run.