Compiler Design

  Program in YACC to recognize the language (a^n b , n>=10). (output to say input is valid or not) File Name : pr12.y /* program to check whether the given string is a part of the language a^n b or not */ /* Shows nothing if string is a part of language */ /* shows a message if string is not a part of language */ %{ # 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 of the Above...

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

  Program in 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-...

  Lex program to recognize a valid arithmetic expression // Lex program to recognize a valid arithmetic expression. % { # include < stdio.h > int a = 0 ,b = 0 ,c = 0 ,d = 0 ,ob = 0 ,cb = 0 ; int flaga = 0 ,flagb = 0 ,flagc = 0 ,flagd = 0 ; % } %% [a - zA - z] + printf( " \n %s is an identifier \n " ,yytext); [ + ] {a ++ ;flaga = 1 ;} [ - ] {b ++ ;flagb = 1 ;} [ * ] {c ++ ;flagc = 1 ;} [ / ] {d ++ ;flagd = 1 ;} [(] ob ++ ; [)] cb ++ ; %% main() { printf( "Enter expression:" ); yylex(); if (ob == cb) printf( " \n valid expression \n " ); else printf ( "invalid expression \n " ); printf( "Addition=%d \t Subtract=%d \n Multiply=%d \t Divide=%d \n " ,a,b,c,d); printf( " \n Operators used: \n " ); if (flaga == 1 ) printf( "+ \t " ); if (flagb == 1 ) printf( "- \t " ); if (flagc == 1 ) printf( "* \t " ); if (flagd == 1 ) printf( "/ \n " ); } // Output of the above program ...

  Lex specification program that generates a C program which takes a string “abcd” and prints the 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 ch; 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 the above program Lex specification program that generates a C program which takes a string “abcd” and prints the pattern

  Lex program to count the number of words,small and capital letters, digits and special characters in a C file /*Lex program to count the number of words, characters, blank spaces and lines in a C file.*/     %{ #include<stdio.h> int lines= 0 , words= 0 ,s_letters= 0 ,c_letters= 0 , num= 0 , spl_char= 0 ,total= 0 ; %}    %% \ n { lines++; words++;} [ \ t ' ' ] words++; [A-Z] c_letters++; [a-z] s_letters++; [ 0 - 9 ] num++; . spl_char++; %% main( void ) { yyin= fopen( "abc.txt" , "r" ); yylex(); total=s_letters+c_letters+num+spl_char; printf( " This File contains ..." ); printf( "\n\t%d lines" , lines); printf( "\n\t%d words" ,words); printf( "\n\t%d small letters" , s_letters); printf( "\n\t%d capital letters" ,c_letters); printf( "\n\t%d digits" , num); printf( "\n\t%d special characters" ,spl_char); printf( "\n\tIn total %d characters.\n" ,total); } int yywrap() { ...

  Lex program to count the number of identifiers //Lex program to count the number of identifiers %{ # include<iostream.h> int count= 0 ; char ch= 0 ; %} digit[ 0 - 9 ] letter[a-zA-Z_] %% {letter}({letter}|{digit})* { count++; } %% int main() { yylex(); printf( "count: %d" ,count); return 0 ; }    // Output of the above Program Lex program to count the number of identifiers

  Lex program that distinguishes keywords, integers, floats, identifiers, operators, and comments /*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( void ) { int result; int running = 1 ; while (running) { result = yylex(); switch (result) { case INTEGER: printf( "integer" ); break ; case FLOAT: printf( "float" ); break ; case OPERATOR: printf( "operator" ); break ; case IDENTIFIER:printf( "identifier" ); break ; case COMMENT: printf( "co...

  Lex program to find the length of the 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 k= 0 ; %} %% [a-zA-Z]+ { if (yyleng>k) { k= yyleng; } } %% int main( int argc[], char **argv[]) { yyin=fopen( "abc.txt" , "r" ); yylex(); printf( "largest: %d" ,k); printf( "\n" ); return 0 ; }     //file abc.txt   Lex program to find the length of the longest word //Output of the above program Lex program to find the length of the longest word

  Lex program that implements the 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 ch = yytext[ 0 ]; ch += 3 ; if (ch> 'z' ) ch -= ( 'z' + 1 - 'a' ); printf ( "%c" ,ch ); } [A-Z] { char ch = yytext[ 0 ] ; ch += 3 ; if (ch> 'Z' ) ch -= ( 'Z' + 1 - 'A' ); printf( "%c" ,ch); } %%   // Output of the above program Caesar cipher

  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 < studio . h > int n_char = 0 ; int n_lines = 0 ; %} %% \ n {++ n_lines , ++ n_char ;} . ++ n_char ; %% int main ( int argc [], char * argv []) { yyin = fopen ( "abc.txt" , "r" ); yylex (); printf ( "n# of characters: %d" , n_char ); printf ( "\n" ); printf ( "n# of lines: %d" , n_lines ); printf ( "\n" ); return 0 ; }   // file abc.txt Lex Program to Count the Number of Lines and Characters in the Input File   // Output of the above program   Lex Program to Count the Number of Lines and Characters in the Input File