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Friday, 24 May 2013

C code to implement Lexical Analyzer

C program to implement Lexical Analyzer

#include<stdio.h> 
#include<string.h> 
#include<stdlib.h>

void removeduplicate(); 
void final();
int Isiden(char ch);
int Isop(char ch);
int Isdel(char ch);
int Iskey(char * str);
void removeduplicate();

char op[8]={'+','-','*','/','=','<','>','%'}; 
char del[8]={'}','{',';','(',')','[',']',','}; 
char *key[]={"int","void","main","char","float"}; 

//char *operato[]={"+","-","/","*","<",">","=","%","<=",">=","++"}; 

int idi=0,idj=0,k,opi=0,opj=0,deli=0,uqdi=0,uqidi=0,uqoperi=0,kdi=0,liti=0,ci=0; 
int uqdeli[20],uqopi[20],uqideni[20],l=0,j; 
char uqdel[20],uqiden[20][20],uqop[20][20],keyword[20][20]; 
char iden[20][20],oper[20][20],delem[20],litral[20][20],lit[20],constant[20][20]; 

void lexanalysis(char *str) 
 { 
   int i=0; 
   while(str[i]!='\0') 
    { 
     if(Isiden(str[i]))     //for identifiers 
       { 
          while(Isiden(str[i])) 
        { 
            iden[idi][idj++]=str[i++]; 
        } 
          iden[idi][idj]='\0'; 
          idi++;idj=0; 
       } 
      else 
      if(str[i]=='"')         //for literals 
         { 
         lit[l++]=str[i]; 
         for(j=i+1;str[j]!='"';j++) 
           { 
            lit[l++]=str[j]; 
           } 
         lit[l++]=str[j];lit[l]='\0'; 
         strcpy(litral[liti++],lit); 
         i=j+1; 
         } 
      else 
      if(Isop(str[i]))        // for operators 
          { 
         while(Isop(str[i])) 
            { 
             oper[opi][opj++]=str[i++]; 
            } 
         oper[opi][opj]='\0'; 
         opi++;opj=0; 
          } 
       else 
       if(Isdel(str[i]))     //for delemeters 
          { 
          while(Isdel(str[i])) 
            { 
              delem[deli++]=str[i++]; 
            } 
           } 
        else 
           { 
            i++; 
        } 
     } 

   removeduplicate(); 
   final(); 
} 

int Isiden(char ch) 
 { 
   if(isalpha(ch)||ch=='_'||isdigit(ch)||ch=='.') 
   return 1; 
   else 
   return 0; 
 } 

int Isop(char ch) 
 { 
  int f=0,i; 
  for(i=0;i<8&&!f;i++) 
   { 
    if(ch==op[i]) 
     f=1; 
   } 
 return f; 
} 

int Isdel(char ch) 
 { 
  int f=0,i; 
  for(i=0;i<8&&!f;i++) 
   { 
    if(ch==del[i]) 
     f=1; 
   } 
 return f; 
 } 

int Iskey(char * str) 
{ 
  int i,f=0; 
  for(i=0;i<5;i++) 
   { 
    if(!strcmp(key[i],str)) 
      f=1; 
    } 
  return f; 
} 

void removeduplicate() 
 { 
   int i,j; 
   for(i=0;i<20;i++) 
    { 
     uqdeli[i]=0; 
     uqopi[i]=0; 
     uqideni[i]=0; 
    } 
   for(i=1;i<deli+1;i++)  //removing duplicate delemeters 
     { 
       if(uqdeli[i-1]==0) 
     { 
           uqdel[uqdi++]=delem[i-1]; 
           for(j=i;j<deli;j++) 
          { 
               if(delem[i-1]==delem[j]) 
                uqdeli[j]=1; 
          } 
      } 
     } 

    for(i=1;i<idi+1;i++)  //removing duplicate  identifiers 
       { 
      if(uqideni[i-1]==0) 
         { 
        strcpy(uqiden[uqidi++],iden[i-1]); 
        for(j=i;j<idi;j++) 
         { 
            if(!strcmp(iden[i-1],iden[j])) 
               uqideni[j]=1; 
         } 
          } 
    } 

     for(i=1;i<opi+1;i++)  //removing duplicate  operators 
     { 
        if(uqopi[i-1]==0) 
           { 
           strcpy(uqop[uqoperi++],oper[i-1]); 
           for(j=i;j<opi;j++) 
             { 
               if(!strcmp(oper[i-1],oper[j])) 
                 uqopi[j]=1; 
             } 
           } 
     } 

 } 
void final() 
 { 
  int i=0; 
  idi=0; 
  for(i=0;i<uqidi;i++) 
   { 
     if(Iskey(uqiden[i]))        //identifying keywords 
     strcpy(keyword[kdi++],uqiden[i]); 
     else 
      if(isdigit(uqiden[i][0]))    //identifying constants 
     strcpy(constant[ci++],uqiden[i]); 
     else 
     strcpy(iden[idi++],uqiden[i]); 
   } 

// printing the outputs 

printf("\n\tDelemeter are : \n"); 
for(i=0;i<uqdi;i++) 
printf("\t%c\n",uqdel[i]); 

printf("\n\tOperators are : \n"); 
for(i=0;i<uqoperi;i++) 
 { 
 printf("\t"); 
 puts(uqop[i]); 
 } 

printf("\n\tIdentifiers are : \n"); 
for(i=0;i<idi;i++) 
 { 
  printf("\t"); 
  puts(iden[i]); 
 } 

printf("\n\tKeywords are : \n"); 
for(i=0;i<kdi;i++) 
 { 
  printf("\t"); 
  puts(keyword[i]); 
 } 

printf("\n\tConstants are :\n"); 
for(i=0;i<ci;i++) 
  { 
  printf("\t"); 
  puts(constant[i]); 
  } 

printf("\n\tLiterals are :\n"); 
for(i=0;i<liti;i++) 
 { 
   printf("\t"); 
   puts(litral[i]); 
 } 
} 
void main() 
{ 
  char str[50]; 
  //clrscr(); 
  printf("\nEnter the string : "); 
  scanf("%[^\n]c",str);
  lexanalysis(str); 
  //getch(); 
}

Output:-


C code to implement Lexical Analyzer

Related Programs:-

Find out First and Follow in a given Grammar

Regular Grammar

SLR Parser

Context Free Grammar (CFG)

DFA (Deterministic Finite Automata)

17 comments:

  1. isop should have prototype

    ReplyDelete
  2. Declare all function before lexicalanalysis() function.

    ReplyDelete
  3. using automata while implementing lexical analyser is much simple and easy to understand, i think this is a simple "checking" program ..... not an efficient one....

    ReplyDelete
  4. Updated programs as feedback given by all above users...thanks to all.

    ReplyDelete
    Replies
    1. Help me isalpha not found

      Delete
    2. not found is alpha and isdigit

      Delete
  5. This comment has been removed by the author.

    ReplyDelete
  6. can you make it read more than just one line? or like make it read from a txt file? that would be much appreciated

    ReplyDelete
  7. can you make it read more than just one line? or like make it read from a txt file? that would be much appreciated

    ReplyDelete
  8. This comment has been removed by the author.

    ReplyDelete
  9. isalpha and isdigit not works!

    ReplyDelete
  10. You don't know a thing about lexical analyzer. why this stupid format of output? what use this can be in the later steps of the compilation?

    ReplyDelete
    Replies
    1. Its just an implementation example.Not an actual lexical analyzer.

      Delete
  11. void lexanalysis(char *str)
    i can not understand its operation and it

    ReplyDelete

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