Program in YACC to recognize the language (a^n b , n>=10). (output to say input is valid or not)

/* program to check whether the given string is  a part of the language a^n b or not */

File Name : pr12.y

%{

 #include<stdio.h>

 int yylex(void);

 int yyerror(char *);

 %}

%token A B   //tokens : the alphabets of language 'a' and 'b' 

%%

//production rules for grammar

expr: s B         

  ;

s : s A 

| A   

;

%%

int main()

{

 

 printf("Enter the string \n");

 yyparse(); 

 return 0;

}

int yyerror(char *s)

{

 printf("Invalid: Not a part of the language - a^n b \n");

}

File Name : pr12.l

%{

 #include "y.tab.h"

 extern int yylval;

%}

A [a]

B [b]

%%

{A} {yylval=yytext[0];return A;}

{B} {yylval=yytext[1];return B;}

\n {return 0;}

. {return yytext[0];}

%%

Output:

YACC to recognize the string „abbb^n, „ab^n „a^n of the langauge (a^n b^n , n>=1)

/*Program in YACC to recognize the string „abbb^n, „ab^n „a^n of the langauge (a^n b^n , n>=1) */
File Name : pr11.y

%{
 #include<stdio.h>
 int yylex(void);
 int yyerror(char *); 
%}
%token A B

%%

statement : expr 
;
expr :A expr B
| A B   
;

%%

int main()
{
 printf("Enter the string :");
 yyparse();
 return 0;
}
int yyerror(char *s)
{
 printf("Invalid");
}

File Name : pr11.l

%{
 #include "y.tab.h"
 extern int yylval;
%}
A [a]
B [b]
%%

{A} {yylval=yytext[0];return A;}
{B} {yylval=yytext[1];return B;}
\n {return 0;}
. {return yytext[0];}

%%



//output of this code

YACC to evaluate an expression (simple calculator program for addition and subtraction, multiplication, division)

/*Program in YACC to evaluate an expression (simple calculator program for addition and

subtraction, multiplication, division).*/

File Name : calc10.y

%{

 #include<stdio.h>

int yylex(void);

int yyerror(char *);

%}

%token NAME NUMBER

%%

statement : NAME '=' expression

 | expression { printf("=%d\n",$1);}

 ;

expression:expression'+' NUMBER{$$ = $1+$3;}

 |expression '-' NUMBER {$$ = $1-$3;}

 |expression '*' NUMBER {$$ = $1*$3;}

 |expression '/' NUMBER { if ($3!=0){ $$ = $1/$3; }else { printf("Error: divide by Zero"); } }

 |NUMBER {$$=$1;}

 ;

%%

int main()

{

yyparse();

return 0;

}

int yyerror(char *s)

{

 printf("%s",s);

}

File Name : calc10.l

%{

 #include "y.tab.h"

 extern int yylval;

%}

%%

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

\n  {return 0;}

.   {return yytext[0];}

%%

Output:

Lex program to recognize a valid arithmetic expression.

//Lex program to recognize a valid arithmetic expression.

%{

#include<stdio.h>

int p=0,q=0,r=0,s=0,ob=0,cb=0;

int flagp=0,flagq=0,flagr=0,flags=0;

%}

%%

[a-zA-z]+ printf("\n %s is an identifier\n",yytext);

[+] {p++;flagp=1;}

[-] {q++;flagq=1;}

[*] {r++;flagr=1;}

[/] {s++;flags=1;}

[(] ob++;

[)] cb++;

%%

void main()

{

printf("Enter expression:");

yylex();

if(ob==cb)

printf("\nvalid expression\n");

else

printf("invalid expression\n");

printf("Addition=%d\tSubtract=%d\nMultiply=%d\tDivide=%d\n",p,q,r,s);

printf("\n Operators used:\n");

if(flagp==1)

printf("+\t");

if (flagq==1)

printf("-\t");

if(flagr==1)

printf("*\t");

if(flags==1)

printf("/\n");

}

//output of this code

Lex specification program that generates a C program which takes a string “abcd" and generates pattern

Lex specification program that generates a C program which takes a string “abcd" and generates pattern

/*Write a Lex specification program that generates a C program which takes a string

“abcd” and prints the following output.

        abcd

        abc

        ab

        a

*/

%{ 

#include<stdio.h>

char i,j;

%}

%%

[a-z]* { for(i='d';i>=1;--i)

      {

           for(j='a';j<=i;++j)

           {

              printf("%c ",j);

           }

          printf("\n");

      }

}

%%

int main()

{

 yylex();

 return 0;

}

//output of this code

Lex program to count the number of words, characters, blank spaces and lines in a file

/*Lex program to count the number of words, characters, blank spaces and lines in a C file.*/

 

 

%{

#include<stdio.h>

int count_lines=0, count_words=0,count_letters=0,S_letters=0, count_num=0, count_char=0,total=0;

%} 

 

%%

\n { count_lines++; count_words++;}

[\t ' '] count_words++;

[A-Z] c_letters++;

[a-z] s_letters++;

[0-9] count_num++;

. count_char++;

%%

void main()

{

yyin= fopen("abc.txt","r");

yylex();

total=s_letters+count_letters+count_num+count_char;

printf(" This File contains ...");

printf("\n\t%d lines", count_lines);

printf("\n\t%d words",count_words);

printf("\n\t%d small letters", s_letters);

printf("\n\t%d capital letters",count_letters);

printf("\n\t%d digits", count_num);

printf("\n\t%d special characters",count_char);

printf("\n\tIn total %d characters.\n",total);

}

 

int yywrap()

{

return(1);

} 

//abc.txt file

output :

Lex program to count the number of identifiers

//Lex program to count the number of identifiers

%{

#include<iostream.h>

int count_identifiers=0;

%}

digit[0-9]

letter[a-zA-Z_]

%%

{letter}({letter}|{digit})* {

 count_identifiers++;

}

%%

int main()

{

 yylex();

 printf("count: %d",count_identifiers);

 return 0;

} 

output:

Lex program that distinguishes keywords, integers, floats, identifiers, operators, and comments in any simple programming language

/*Lex program that distinguishes keywords, integers, floats, identifiers, operators, and

comments in any simple programming language.*/ 

 %{

enum{INTEGER,FLOAT,IDENTIFIER,OPERATOR,COMMENT};

%}

digit [0-9]

letter[A-Za-z_]

%%

" "|"\t" ;

{digit}+   { return INTEGER; }

{digit}+\.{digit}+ { return FLOAT; }

'+' |

'-' |

'*' |

'/' { return OPERATOR; }

{letter}({letter}|{digit})* { return IDENTIFIER; }

"/*" { return COMMENT;}

%%

int main()

{

  int output1;

  int main_run = 1;

 while(main_run)

 {

  result = yylex();

  switch(output1)

 {

  case INTEGER: printf("integer"); 

                break;

  case FLOAT: printf("float"); 

                break;

  case OPERATOR: printf("operator");

                break;

  case IDENTIFIER:printf("identifier"); 

                break;

  case COMMENT: printf("comment");

                break;

  }

 }

return 0;

}

output:

Lex program that finds the lenght of longest word

/*Write a Lex program that finds the length of the longest word (defined as a contiguous

 string of upper and lower case letters) in the input.*/

 

%{ 

#include<stdio.h>

int longest_word=0;

%}

%%

[a-zA-Z]+ {

if(yyleng>k)

{  longest_word= yyleng;

}

}

%%

int main()

{

 yyin=fopen("abc.txt","r");

 yylex(); 

 printf("largest: %d",longest_word);

 printf("\n");

 return 0;

}

// abc.txt file

output:

Lex Program that implements Caesar Cipher

/* Write a Lex program that implements the Caesar cipher: it replaces every letter 

with the one three letters after in in alphabetical order, wrapping around at Z.

e.g. a is replaced by d, b by e, and so on z by c.  */ 

 

%%

[a-z] {char cipher_char = yytext[0];

cipher_char += 3;

if (cipher_char> 'z') cipher_char -= ('z'+1- 'a');

printf ("%c" ,cipher_char );

}

[A-Z] { char cipher_char = yytext[0] ;

cipher_char += 3;

if (cipher_char> 'Z') cipher_char -= ('Z'+1- 'A');

printf("%c",cipher_char);

}

%%

/*Output of this program*/

Lex Program to Count the Number of Lines and Characters in the Input File

//Lex Program to Count the Number of Lines and Characters in the Input File

 

%{ 

  #include<stdio.h>

  int no_of_char=0;

  int no_of_lines=0;

%}

%%

\n {++no_of_lines, ++no_of_char;}

. ++no_of_char;

%%

int main()

{

 yyin=fopen("abc.txt", "r"); 

 yylex();

 printf("n0 of characters: %d",no_of_char);

 printf("\n");

 printf("n0 of lines: %d",no_of_lines);

 printf("\n"); 

 return 0;

}

//abc.txt file

output: