7.FOLLOW.c

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

int nop, m = 0;
char prod[10][10], res[10];

void FIRST(char c);
void FOLLOW(char c);
void result(char c);

int main()
{
	int i;
	int choice;
	char c;

	printf("Enter the no. of productions : ");
	scanf("%d", &nop);
	puts("\nEnter the production string like \"E=E+T\" \nand epsilon as #\n");

	for (i = 0; i < nop; ++i)
	{
		printf("Enter production Number %d : ", i + 1);
		scanf("%s", prod[i]);
	}
	do
	{
		m = 0;
		memset(res, '\0', sizeof(res));

		printf("\nFind FOLLOW of --> ");
		scanf(" %c", &c);

		if (isupper(c))
			FOLLOW(c);
		else
		{
			printf("Not Possible");
			return 0;
		}

		printf("Follow (%c) = { ", c);
		for (i = 0; i < m; ++i)
			printf("%c ", res[i]);
		puts(" }");

		printf("Do you want to continue(Press 1 to continue...) ? ");
		scanf("%d", &choice);
	} while (choice == 1);

	return 0;
}

void FOLLOW(char c)
{
	int i, j;
	if (prod[0][0] == c)
		result('$');
	for (i = 0; i < nop; ++i)
	{
		for (j = 2; j <= strlen(prod[i]); ++j)
		{
			if (prod[i][j] == c)
			{
				if (prod[i][j + 1] != '\0')
					FIRST(prod[i][j + 1]);
				if (prod[i][j + 1] == '\0' && c != prod[i][0])
					FOLLOW(prod[i][0]);
			}
		}
	}
	return;
}

void FIRST(char c)
{
	int k;
	if (!(isupper(c)))
		result(c);
	for (k = 0; k < nop; ++k)
	{
		if (prod[k][0] == c)
		{
			if (prod[k][2] == '#')
				FOLLOW(prod[k][0]);
			else if (prod[k][2] == c)
				return;
			else if (islower(prod[k][2]))
				result(prod[k][2]);
			else
				FIRST(prod[k][2]);
		}
	}
	return;
}

void result(char c)
{
	int i;
	for (i = 0; i <= m; ++i)
		if (res[i] == c)
			return;
	res[m++] = c;
}

/*
	Input/ Output :-
	-------------

	Enter the no. of productions : 8

	Enter the production string like "E=E+T"
	and epsilon as #

	Enter production Number 1 : E=TX
	Enter production Number 2 : X=+TX
	Enter production Number 3 : X=#
	Enter production Number 4 : T=FY
	Enter production Number 5 : Y=*FY
	Enter production Number 6 : Y=#
	Enter production Number 7 : F=(E)
	Enter production Number 8 : F=i

	Find FOLLOW of --> E
	Follow (E) = { $ )  }
	Do you want to continue(Press 1 to continue...) ? 1

	Find FOLLOW of --> X
	Follow (X) = { $ )  }
	Do you want to continue(Press 1 to continue...) ? 1

	Find FOLLOW of --> T
	Follow (T) = { + $ )  }
	Do you want to continue(Press 1 to continue...) ? 1

	Find FOLLOW of --> Y
	Follow (Y) = { + $ )  }
	Do you want to continue(Press 1 to continue...) ? 1

	Find FOLLOW of --> F
	Follow (F) = { * + $ )  }
	Do you want to continue(Press 1 to continue...) ? 0
*/