Intermediate Code Generator for Arithmetic Expression - Yacc Program - Compiler Lab

Program:

(Lex Program : intar.l)

ALPHA [A-Za-z]
DIGIT [0-9]
%%

{ALPHA}({ALPHA}|{DIGIT})* return ID;
{DIGIT}+ {yylval=atoi(yytext); return NUM;}
[\n\t] yyterminate();
. return yytext[0];
%%

(Yacc Program : intar.y)

%token ID NUM
%right '='
%left '+' '-'
%left '*' '/'
%left UMINUS
%%

S : ID{push();} '='{push();} E{codegen_assign();}
   ;
E : E '+'{push();} T{codegen();}
   | E '-'{push();} T{codegen();}
   | T
   ;
T : T '*'{push();} F{codegen();}
   | T '/'{push();} F{codegen();}
   | F
   ;
F : '(' E ')'
   | '-'{push();} F{codegen_umin();} %prec UMINUS
   | ID{push();}
   | NUM{push();}
   ;
%%

#include "lex.yy.c"
#include<ctype.h>
char st[100][10];
int top=0;
char i_[2]="0";
char temp[2]="t";

main()
 {
 printf("Enter the expression : ");
 yyparse();
 }

push()
{
  strcpy(st[++top],yytext);
 }

codegen()
 {
 strcpy(temp,"t");
 strcat(temp,i_);
  printf("%s = %s %s %s\n",temp,st[top-2],st[top-1],st[top]);
  top-=2;
 strcpy(st[top],temp);
 i_[0]++;
 }

codegen_umin()
 {
 strcpy(temp,"t");
 strcat(temp,i_);
 printf("%s = -%s\n",temp,st[top]);
 top--;
 strcpy(st[top],temp);
 i_[0]++;
 }

codegen_assign()
 {
 printf("%s = %s\n",st[top-2],st[top]);
 top-=2;
 }


Output:

nn@linuxmint ~ $ lex intar.l
nn@linuxmint ~ $ yacc intar.y
nn@linuxmint ~ $ gcc y.tab.c -ll -ly
nn@linuxmint ~ $ ./a.out
Enter the expression : a=(k+8)*(c-s)
t0 = k + 8
t1 = c - s
t2 = t0 * t1
a = t2
nn@linuxmint ~ $