First n Follow

Please download to get full document.

View again

of 4
15 views
DOCX
All materials on our website are shared by users. If you have any questions about copyright issues, please report us to resolve them. We are always happy to assist you.
Document Description
Program to find first and follow
Document Share
Documents Related
Document Tags
Document Transcript
  import java.util.*; import java.io.*; class fstnflw { static char ntermnl[],termnl[]; static int ntlen,tlen; static String grmr[][],fst[],flw[]; public static void main(String args[]) throws IOException { String nt,t; int i,j,n; BufferedReader br=new BufferedReader(new InputStreamReader(System.in)); System.out.println( Enter the non-terminals ); nt=br.readLine(); ntlen=nt.length(); ntermnl=new char[ntlen]; ntermnl=nt.toCharArray(); System.out.println( Enter the terminals ); t=br.readLine(); tlen=t.length(); termnl=new char[tlen]; termnl=t.toCharArray(); System.out.println( Specify the grammar(Enter 9 for epsilon production) ); grmr=new String[ntlen][]; for(i=0;i<ntlen;i++) { System.out.println( Enter the number of productions for +ntermnl[i n=Integer.parseInt(br.readLine()); grmr[i]=new String[n]; System.out.println( Enter the productions ); for(j=0;j<n;j++) grmr[i][j]=br.readLine(); } fst=new String[ntlen]; for(i=0;i<ntlen;i++) fst[i]=first(i); System.out.println( First Set ); for(i=0;i<ntlen;i++) System.out.println(removeDuplicates(fst[i])); flw=new String[ntlen]; for(i=0;i<ntlen;i++) flw[i]=follow(i); System.out.println( Follow Set ); for(i=0;i<ntlen;i++) System.out.println(removeDuplicates(flw[i])); } static String first(int i) {  int j,k,l=0,found=0; String temp= ,str= ; for(j=0;j<grmr[i].length;j++) //number of productions { for(k=0;k<grmr[i][j].length();k++,found=0) //when nonterminal has epsilon production { for(l=0;l<ntlen;l++) //finding nonterminal { if(grmr[i][j].charAt(k)==ntermnl[l]) //for nonterminal in first set { str=first(l); if(!(str.length()==1 && str.charAt(0)=='9')) //when epsilon production is the only nonterminal production temp=temp+str; found=1; break; } } if(found==1) { if(str.contains( 9 )) //here epsilon will lead to next nonterminal’s first set  continue; } else //if first set includes terminal temp=temp+grmr[i][j].charAt(k); break; } } return temp; } static String follow(int i) { char pro[],chr[]; String temp= ; int j,k,l,m,n,found=0; if(i==0) temp= $ ; for(j=0;j<ntlen;j++) { for(k=0;k<grmr[j].length;k++) //entering grammar matrix { pro=new char[grmr[j][k].length()]; pro=grmr[j][k].toCharArray(); for(l=0;l<pro.length;l++) //entering each production { if(pro[l]==ntermnl[i]) //finding the nonterminal whose follow set is to be found { if(l==pro.length-1) //if it is the last terminal/non-terminal then follow of current non-terminal {  if(j<i) temp=temp+flw[j]; } else { for(m=0;m<ntlen;m++) { if(pro[l+1]==ntermnl[m]) //first of next non-terminal otherwise (else later…)  { chr=new char[fst[m].length()]; chr=fst[m].toCharArray(); for(n=0;n<chr.length;n++) { if(chr[n]=='9') //if first includes epsilon { if(l+1==pro.length-1) temp=temp+follow(j); //when non-terminal is second last else temp=temp+follow(m); } else temp=temp+chr[n]; //include whole first set except epsilon } found=1; } } if(found!=1) temp=temp+pro[l+1]; //follow set will include terminal(else is here) } } } } } return temp; } static String removeDuplicates(String str) { int i; char ch; boolean seen[] = new boolean[256]; StringBuilder sb = new StringBuilder(seen.length); for(i=0;i<str.length();i++) { ch=str.charAt(i); if (!seen[ch]) { seen[ch] = true; sb.append(ch);  } } return sb.toString(); } } /* OUTPUT: student@admini:~/Desktop/c229899$ javac ff.java student@admini:~/Desktop/c229899$ java fstnflw Enter the non-terminals SABC Enter the terminals ab Specify the grammar(Enter 9 for epsilon production) Enter the number of productions for S 1 Enter the productions aABC Enter the number of productions for A 2 Enter the productions a bb Enter the number of productions for B 2 Enter the productions a 9 Enter the number of productions for C 2 Enter the productions b 9 First Set a ab a9 b9 Follow Set $ ab$ b$ $ */
Search Related
We Need Your Support
Thank you for visiting our website and your interest in our free products and services. We are nonprofit website to share and download documents. To the running of this website, we need your help to support us.

Thanks to everyone for your continued support.

No, Thanks