sym_tab.y

Symbol table program using linked list..contains yacc & lex files

%{

#include<stdio.h>

struct node

        {

        char symbol;

        int  value;

        struct node *link;

        }*first;

%}

%start S

%union {

        char name;

        int value;

       }

%token <name> LETTER

%token <value> DIGIT

%token ENDLINE

%type <value> exp

%type <value> stmt

%left '+' '-' '*' '/'  

%left '='

%%



 S      :       stmt

                {}

        ;



 stmt   :       LETTER '=' exp ENDLINE {assign($1,$3);} stmt

                {}
        

        |       exp ENDLINE

                { printf("The Value Of The Expression Is :: %d\n",$1); 
                }

        ;



 exp    :       LETTER

                { $$=lookup($1); }

        |       DIGIT

                { $$=$1; }

        |       exp '+' exp

                { $$ = $1 + $3;}
        |       exp '-' exp

                { $$ = $1 - $3;}

        |       exp '*' exp

                { $$ =  $1 * $3; }

        |       exp '/' exp

                { $$ = $1 / $3;}
        |       '(' exp ')'

                { $$=$2; }

        ;

%%

main()

{

	return (yyparse());

}

yyerror(s)

char *s;

{

        fprintf(stderr,"\n%s",s);

}

yywrap()

{

        return 1;

}



void assign(char c,int v)

{

   struct node *t = (struct node*) malloc (sizeof(struct node) );

  
       

          if(first == NULL)

                 {

                   first=(struct node*) malloc(sizeof(struct node));

                   first->symbol=c;

                   first->value=v;

                   first->link=NULL;

                 }

         else

                 {

                   t->symbol=c;

                   t->value=v;

           	   t->link=first;

                   first=t;

                 }

         printf("Symbol %c with value %d inserted\n",first->symbol,first->value);

	 

      



 }



int lookup(char c)

{

    struct node *t = first;

    while(first != NULL)

       {

          if(t->symbol == c)

             {

                    printf("Symbol %c is in symbol table & its value is %d\n",t->symbol,t->value);
                return t->value;

             }

          else

                t=t->link;

       }

    return (0);

}