madhi43 / ex-5-recognition-of-a-valid-arithmetic-expression-that-uses-operator---and-using-yacc

Ex-5-RECOGNITION-OF-A-VALID-ARITHMETIC-EXPRESSION-THAT-USES-OPERATOR-AND-USING-YACC

Date:07.03.24

AIM

To write a yacc program to recognize a valid arithmetic expression that uses operator +,- ,* and /.

ALGORITHM

1. Start the program.
2. Write a program in the vi editor and save it with .l extension.
3. In the lex program, write the translation rules for the operators =,+,-,*,/ and for the identifier.
4. Write a program in the vi editor and save it with .y extension.
5. Compile the lex program with lex compiler to produce output file as lex.yy.c. eg $ lex filename.l
6. Compile the yacc program with yacc compiler to produce output file as y.tab.c. eg $ yacc –d arith_id.y
7. Compile these with the C compiler as gcc lex.yy.c y.tab.c
8. Enter an arithmetic expression as input and the tokens are identified as output.

PROGRAM

com.|.txt

%{ 
/* 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-zA-Z]*[0-9]* { 
printf("\n Identifier is %s",yytext); 
return ID; } 
. return yytext[0]; 
\n return 0; 
%% 
int yywrap() 
{ 
return 1; 
}

com.y.txt

%{ 
#include <stdio.h> 
/* This YACC program is for recognizing the Expression */ 
%} 
%token A ID 
%% 
statement: A'='E 
| E { 
printf("\n Valid arithmetic expression"); 
$$=$1; 
} 
; 
  E: E'+'ID 
| E'-'ID 
| E'*'ID 
| E'/'ID 
| ID 
; 
%% 
extern FILE*yyin; 
int main() { 
do { 
yyparse(); 
}while(!feof(yyin)); } 
yyerror(char*s) 
{ 
}

OUTPUT

RESULT

A YACC program to recognize a valid arithmetic expression that uses operator +,-,* and / is executed successfully and the output is verified.