/* 1a. Write a program in LEX to count the number of vowels and consonants in a given string. */

%{/* No. of Vowels, Consonants & Blank characters */ int nvow=0,ncons=0,nblank=0;%}

%%[aeiouAEIOU] nvow++;                              /* Increment the no. of Vowels */[b-df-hj-np-tv-zB-DF-HJ-NP-TV-Z] ncons++; /* Increment the no. of Consonants */[ ] nblank++;                                          /* Increment the no. of BlankSpace */%%

#include"stdio.h"int main(){    printf("\nEnter the string : ");    yylex();    printf("\n\nNo. of Vowels = %d",nvow);    printf("\n\nNo. of Consonants = %d",ncons);    printf("\n\nNo. of Blank Spaces = %d\n",nblank);    return 0;}

 2a. Write a LEX program to count number of lines, words, characters and blank spaces */

%{int cha=0;int words=0;int lines=0;int blanks=0;%}

%%\n lines++ ; [ \t] cha++; blanks++;[a-zA-Z0-9] cha++;[a-zA-Z0-9]/[ \n] words++; cha++;. cha++;%%

main(){    yylex();    printf("characters=%d\n",cha);    printf("words=%d\n",words);    printf("lines=%d\n",lines);    printf("blanks=%d\n",blanks);}

 3a. Write a LEX program to count the number of positive & negative integers and fractions */          %{#include"stdio.h"int posnum=0;int negnum=0;int posfra=0;int negfra=0;%}dig [0-9]

%%\+?{dig}+ posnum++;-{dig}+ negnum++;\+?{dig}*\.{dig}+([eE][-+?]?{dig}+)? posfra++;-{dig}*\.{dig}+([eE][+-]?{dig}+)? negfra++;%%

main(){    yylex();    printf("%d",negnum);

    printf("\n%d",posnum);    printf("\n%d",posfra);    printf("\n%d",negfra);}

 

5a. Write a LEX program to count number of printf's and scanf's in a given program */

%{#include"stdio.h"int pcount=0;int scount=0;%}

%%"printf" fprintf(yyout,"write");pcount++;"scanf" fprintf(yyout,"read");scount++;%%

main(){    yyin=fopen("tester.c","r");    yyout=fopen("otester","w");    yylex();    printf("\nprintf count=%d\nscanf count=%d\n",pcount,scount);    fclose(yyin);    fclose(yyout);}

 8a. Write a LEX program to count the number of identifiers */

%{int id_ct=0;%}

SPC [ \t]*IDE [a-zA-Z_][a-zA-Z0-9_]*DEC "int "|"float "|"char "|"long "|"unsigned "%s DEFN

%%{SPC}{DEC}{SPC} {BEGIN(DEFN);}<DEFN>{IDE}{SPC}\,{SPC} {id_ct++;}<DEFN>{IDE}{SPC}\;{SPC} {id_ct++;BEGIN(INITIAL);}<*>./\n+;.;%%

main(int argc,char *argv[]){    yyin=fopen(argv[1],"r");    yylex();    printf("\nNumber of identifiers is %d\n",id_ct);}

* 7a. Write a LEX program to identify a compound statement */

%{#include"stdio.h"int count=0;%}

%%" [aA][nN][dD] " count ++;" [oO][rR] " count++;" [bB][uU][tT] " count++;%%

main(){yylex();

if( count != 0 )printf("\nIt is a compound statement");elseprintf("\nIts is a Simple statement"); }

 

* 6a. Write a LEX program to recognize a valid arithmetic expression. Count number of operators present and print them seperately. */

%{/* No. of operators and operands */int nop=0,noprnd=0,top=-1,stack[20];%}

%%[0-9]*|[a-zA-Z]* noprnd++; /* Increment no. of operand */[+-/*%] nop++;                /* Increment no. of operator */"(" { stack[++top]='(';}")" { if((stack[top]='(')&&(top!=-1)) top--; }%%

#include"stdio.h"int main(){    printf("\n*** Enter an expression ***\n");    yylex();    if ((nop != (noprnd - 1)) || ( top==-1))        printf("\nIt's an INVALID statement");    else    {        printf("\nIt's a VALID statement");        printf("\nNumber of operators = %d",nop);    }    return 0;}