firstandfollow.c

#include<stdio.h>
#include<math.h>
#include<string.h>
#include<ctype.h>
#include<stdlib.h>
int n,m=0,p,i=0,j=0;
char a[10][10],A[5][6],f[10],c;
void follow(char c);
void first(char c);
int main(){


int i,z;
char c,ch;
//clrscr();
//
FILE *f;
	f=fopen("productions.txt","r");
	//num of productions
	
	for(i=0;i<5;i++){
		while((c=fgetc(f))!='\0'){
			fscanf(f,"%s",&A[i][j]);
			c++;
		}
	}
	for(i=0;i<5;i++){
		for(j=0;j<6;j++){
			a[i][j]=A[i][j];
		}
	}
//
printf("Enter the no of prooductions:\n");
scanf("%d",&n);
printf("Enter the productions:\n");
for(i=0;i<n;i++)
scanf("%s%c",a[i],&ch);
do{
	m=0;
	printf("Enter the elemets whose fisrt & follow is to be found:");
	scanf("%c",&c);
	first(c);
	printf("First(%c)={",c);
	for(i=0;i<m;i++)
	printf("%c",f[i]);
	printf("}\n");
	strcpy(f," ");
	//flushall();
	m=0;
	follow(c);
	printf("Follow(%c)={",c);
	for(i=0;i<m;i++)
	printf("%c",f[i]);
	printf("}\n");
	printf("Continue(0/1)?");
	scanf("%d%c",&z,&ch);
}while(z==1);
return(0);
}
void first(char c)
{
	int k;
	if(!isupper(c))
	f[m++]=c;
	for(k=0;k<n;k++)
	{
	if(a[k][0]==c)
	{
	if(a[k][2]=='$')
	follow(a[k][0]);
	else if(islower(a[k][2]))
	f[m++]=a[k][2];
	else first(a[k][2]);
	}
	}
}
void follow(char c)
{
	if(a[0][0]==c)
	f[m++]='$';
	for(i=0;i<n;i++)
	{
	for(j=2;j<strlen(a[i]);j++)
	{
	if(a[i][j]==c)
	{
	if(a[i][j+1]!='\0')
	first(a[i][j+1]);
	if(a[i][j+1]=='\0' && c!=a[i][0])
	follow(a[i][0]);
	}
	}	
	}
}