7. PARSING OF INPUT STRING TO AN OPG

SOURCE CODE:

#include<stdio.h>

#include<conio.h>

#include<string.h>

#include<ctype.h>

int point(char *sort,char ch)

{

      char *position;

      position=strchr(sort,ch);

      return(position-sort);

}

void main()

{

      char OPM[10][10],prod[10][5],ter[20],nter[20],str[20],hand[10],temp[20];

      char symbol,ch1,ch;

      int i,j,k,cnter,cter,p=4,mx,my,m=0;

      clrscr();

      printf("\nEnter non terminals:");

      scanf("%s",nter);

      printf("\nEnter terminals:");

      scanf("%s",ter);

      cter=strlen(ter);

      printf("\nEnter no of productions: ");

      scanf("%d",&p);

      printf("Enter Productions:-\n");

      for(i=0;i<p;i++)

            scanf("%s",prod[i]);

      printf("\nEnter The OPM Matrix:-\n");

      for(i=0;i<cter;i++)

            scanf("\n%s",OPM[i]);

      printf("\nEnter string For Parsing:-");

      scanf("%s",str);

      int l=0,r=0;

      i=0;

      while(strlen(str)>3)

      {

            ch=str[i];

            symbol=' ';

            if(ch=='#' && i==0)

                  symbol='<';

            else if(ch=='#' && i==(strlen(str)-1))

                  symbol='>';

            else

            {

                  if(!isupper(ch))

                  {

                        mx=point(ter,ch);

                        ch1=str[i+1];

                        if(!isupper(ch1))

                        {

                              r=i+1;

                              my=point(ter,ch1);

                              symbol=OPM[mx][my];

                        }

                        else

                        {

                              ch1=str[i+2];

                              if(isupper(ch1))

                              {

                                    printf("\n\nString is not valid");

                                    break;

                              }

                              else

                              {

                                    r=i+2;

                                    if(ch1=='#')

                                          symbol='>';

                                    else

                                    {

                                          my=point(ter,ch1);

                                          symbol=OPM[mx][my];

                                    }

                              }

                        }

                  }

            }

            if(symbol=='<')

            {

                  i++;

                  l=i;

            }

            else if(symbol=='>')

            {

                  printf("\n");

                  if(r-l==1)

                  {

                        for(k=0;k<p;k++)

                              if(str[l]==prod[k][2])

                                    str[l]=prod[k][0];

                        i=0;

                        printf("\n%s",str);

                        getch();

                  }

                  else if((r-l)==3)

                  {

                        ch=str[l+1];

                        for(k=0;k<p;k++)

                        {

                              if(ch==prod[k][3] || (isupper(ch) && isupper(prod[k][3])))

                              {

                                    str[l++]=prod[k][0];

                                    i=0;

                                    for(m=0;str[r]!='\0';m++)

                                    {

                                          temp[m]=str[r];

                                          r++;

                                    }

                                    temp[m]='\0';

                                    str[l]='\0';

                                    str[l+1]='\0';

                                    strcat(str,temp);

                                    printf("\n%s",str);

                              }

                        }

                  }

            }

            else

                  i++;

      }

      getch();

}

Output:

 Enter non terminals:ETF

 Enter terminals:+*()i

 Enter no of productions: 6

 Enter Productions:-

 E=E+T   E=T   T=T*F   T=F   F=(E)  F=i

 Enter The OPM Matrix:-

 ><<><

 >><><

 <<<=<

 >>0>0

 >>0>0

 Enter string For Parsing:-#i+i*(i+i)#

 #F+i*(i+i)#

 #F+F*(i+i)#

 #F+F*(F+i)#

 #F+F*(F+F)#

 #F+F*(E)#

 #F+F*F#

 #F+T#

 #E#