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Generate YACC specification for a few synthetic categories (a)Program to recognize a valid arithmetic expression that uses +,-,* and /. (b) program to recognize a valid variable which starts with a letter followed by any number of letters or digits

 Generate YACC specification for a few synthetic categories

(a)Program to recognize a valid arithmetic expression that uses +,-,* and /. (b) program to recognize a valid variable which starts with a letter followed by any number of letters or digits
a)Program to recognize a valid arithmetic expression that uses +,-,* and /.



Program-

%{ /* This LEX program returns the tokens for the expression */ #include “y.tab.h” %} %% “=” {printf(“\n Operator is EQUAL”);} “+” {printf(“\n Operator is PLUS”);} “-“ {printf(“\n Operator is MINUS”);} “/” {printf(“\n Operator is DIVISION”);} “*” {printf(“\n Operator is MULTIPLICATION”);} [a-z A-Z]*[0-9]* { printf(“\n Identifier is %s”,yytext); return ID; } return yytext[0]; \n return 0; %% int yywrap() { return 1; } Program Name : arith_id.y %{ #include /* This YYAC program is for recognizing the Expression */ %} %% statement: A’=’E | E { printf(“\n Valid arithmetic expression”); $$ = $1; }; E: E’+’ID | E’-’ID | E’*’ID | E’/’ID | ID ; %% extern FILE *yyin; main() { do { yyparse(); }while(!feof(yyin)); } yyerror(char*s) { } Output: [root@localhost]# lex arith_id.1 [root@localhost]# yacc –d arith_id.y [root@localhost]# gcc lex.yy.c y.tab.c [root@localhost]# ./a.out x=a+b; Identifier is x Operator is EQUAL Identifier is a Operator is PLUS Identifier is b

(b) program to recognize a valid variable which starts with a letter followed by any number of
letters or digits

%{
/* This LEX program returns the tokens for the Expression */
#include "y.tab.h"
%}
%%
"int " {return INT;}
"float" {return FLOAT;}
"double" {return DOUBLE;}
[a-zA-Z]*[0-9]*{
printf("\nIdentifier is %s",yytext);
return ID;
}
return yytext[0];
\n return 0;
int yywrap()
{
return 1;
}



Program name: variable_test.y

%{
#include
/* This YACC program is for recognising the Expression*/
%}
%token ID INT FLOAT DOUBLE
%%
D;T L
;
L:L,ID
|ID
;
T:INT
|FLOAT
|DOUBLE
;
%%
extern FILE *yyin;
main()
{
do
{
yyparse();
}while(!feof(yyin));
}
yyerror(char*s)
{
}

Output:

[root@localhost]# lex variable_test.I
[root@localhost]# yacc –d variable_test.y
[root@localhost]# gcc lex.yy.c y.tab.c
[root@localhost]# ./a.out
int a,b;

Identifier is a
Identifier is b[root@localhost]#

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