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Msword CD

The document contains Yacc and Lex code to recognize and evaluate valid arithmetic expressions using the operators +, -, *, and /. The first part defines the lexical analyzer and parser for recognizing expressions, while the second part adds functionality to evaluate the expressions with proper operator precedence. The program also handles error cases such as division by zero and unexpected characters.

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10 views7 pages

Msword CD

The document contains Yacc and Lex code to recognize and evaluate valid arithmetic expressions using the operators +, -, *, and /. The first part defines the lexical analyzer and parser for recognizing expressions, while the second part adds functionality to evaluate the expressions with proper operator precedence. The program also handles error cases such as division by zero and unexpected characters.

Uploaded by

ayushdwdi63
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
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Q22.

Design a yacc/lex code to recognize valid arithmetic expression with operators


+,-,* and /.

Program

(prog.l):

%{

#include "y.tab.h"

%}

%%

[0-9]+ { yylval = atoi(yytext); return NUMBER;


} "+" { return PLUS; }

"-" { return MINUS; }

"*" { return MUL; }

"/" { return DIV; }

[ \t] {}

. { printf("Unexpected character: %s\nINVALID expression", yytext); exit(1); }

%%

int yywrap(){
return 1;
}

(prog.y)

%{

#include <stdio.h>

Ayush Dwivedi Sec- A1 Roll No.


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#include <stdlib.h>

%}

%token NUMBER

%token PLUS MINUS MUL DIV

%%

expr:

expr PLUS expr

| expr MINUS expr

| expr MUL expr

| expr DIV expr


| NUMBER

%%

int yyerror(const char *s)


{ fprintf(stderr, "Error: %s\n",
s); exit(1);
}

int main(){

printf("Enter an arithmetic expression: ");


if(yyparse() == 0){
printf("This is a valid expression\n");

else printf("This expression is invalid\n");


return 0;

Ayush Dwivedi Sec- A1 Roll No.


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OUTPUT:

Ayush Dwivedi Sec- A1 Roll No.


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Q23. Design a yacc/lex code to evaluate arithmetic expression with operators +, -, *, and
/ with operator precedence.

Program
(prog.l):

%{
#include "y.tab.h"

%}

%%

[0-9]+ { yylval = atoi(yytext); return NUMBER;


} [+\-*/] { return yytext[0]; }
"\n" { return '\n'; }

[ \t] { /* Ignore whitespace */ }

. { printf("Unexpected character: %s\nINVALID expression\n", yytext); exit(1); }

%%
int yywrap(){
return 1;
}

(prog.y):

%{

#include <stdio.h>
#include <stdlib.h>
%}

Ayush Dwivedi Sec- A1 Roll No.


15
%token NUMBER

%left '+' '-'

%left '*' '/'

%%

stmt:

expr '\n' { printf("The result is: %d\n", $1); }

;
expr:

expr '+' expr { $$ = $1 + $3; }


| expr '-' expr { $$ = $1 - $3; }

| expr '*' expr { $$ = $1 * $3; }

| expr '/' expr


{ if($3 ==
0){
fprintf(stderr, "Cannot divide by 0\n");
exit(1);
}

else{

$$ = $1 / $3;

| NUMBER { $$ = $1; }

;
%%

int yyerror(const char *s)


{ fprintf(stderr, "Error: %s\n",
s); exit(1);

Ayush Dwivedi Sec- A1 Roll No.


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}

int main(){

printf("Enter an arithmetic expression:\n");


yyparse();
return 0;
}

Output

Ayush Dwivedi Sec- A1 Roll No.


15
Ayush Dwivedi Sec- A1 Roll No.
15

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