PROGRAM 11:
Write
program to find Simulate First and Follow of any given grammar.
ALGORITHM:
finding FIRST
1. If X is terminal, FIRST(X) = {X}. If X → ε is a
production, then add ε to FIRST(X).
2. If X is a non-terminal, and X → Y1 Y2 … Yk is a
production, and ε is in all of FIRST(Y1), …, FIRST(Yk), then add ε to FIRST(X).
3. If X is a non-terminal, and X → Y1 Y2 … Yk is a
production, then add a to FIRST(X) if for some i, a is in FIRST(Yi), and ε is
in all of FIRST(Y1), …, FIRST(Yi-1).
finding FOLLOW
1. FOLLOW(S) = { $ }
// where S is the starting Non-Terminal
2. If A -> pBq is a production, where p, B and q are any
grammar symbols,
then everything in
FIRST(q) except Є is in FOLLOW(B.
3. If A->pB is a production, then everything in FOLLOW(A)
is in FOLLOW(B).
4. If A->pBq is a production and FIRST(q) contains Є,
then FOLLOW(B)
contains { FIRST(q) – Є } U FOLLOW(A)
PROGRAM:
#include<stdio.h>
#include<ctype.h>
#include<string.h>
void followfirst(char, int, int);
void follow(char c);
void findfirst(char, int, int);
int count, n = 0;
char calc_first[10][100];
char calc_follow[10][100];
int m = 0;
char production[10][10];
char f[10], first[10];
int k;
char ck;
int e;
int main(int argc, char **argv)
{
int jm = 0;
int km = 0;
int i, choice;
char c, ch;
count = 8;
strcpy(production[0], "E=TR");
strcpy(production[1], "R=+TR");
strcpy(production[2], "R=#");
strcpy(production[3], "T=FY");
strcpy(production[4], "Y=*FY");
strcpy(production[5], "Y=#");
strcpy(production[6], "F=(E)");
strcpy(production[7], "F=i");
int kay;
char done[count];
int ptr = -1;
for(k = 0; k < count; k++) {
for(kay = 0; kay < 100; kay++) {
calc_first[k][kay] = '!';
}
}
int point1 = 0, point2, xxx;
for(k = 0; k < count; k++)
{
c = production[k][0];
point2 = 0;
xxx = 0;
for(kay = 0; kay <= ptr; kay++)
if(c == done[kay])
xxx = 1;
if (xxx == 1)
continue;
findfirst(c, 0, 0);
ptr += 1;
done[ptr] = c;
printf("\n First(%c) = { ", c);
calc_first[point1][point2++] = c;
for(i = 0 + jm; i < n; i++) {
int lark = 0, chk = 0;
for(lark = 0; lark < point2;
lark++) {
if (first[i] == calc_first[point1][lark])
{
chk = 1;
break;
}
}
if(chk == 0)
{
printf("%c, ",
first[i]);
calc_first[point1][point2++] =
first[i];
}
}
printf("}\n");
jm = n;
point1++;
}
printf("\n");
printf("-----------------------------------------------\n\n");
char donee[count];
ptr = -1;
for(k = 0; k < count; k++) {
for(kay = 0; kay < 100; kay++) {
calc_follow[k][kay] = '!';
}
}
point1 = 0;
int land = 0;
for(e = 0; e < count; e++)
{
ck = production[e][0];
point2 = 0;
xxx = 0;
for(kay = 0; kay <= ptr; kay++)
if(ck == donee[kay])
xxx = 1;
if (xxx == 1)
continue;
land += 1;
follow(ck);
ptr += 1;
donee[ptr] = ck;
printf(" Follow(%c) = { ", ck);
calc_follow[point1][point2++] = ck;
for(i = 0 + km; i < m; i++) {
int lark = 0, chk = 0;
for(lark = 0; lark < point2;
lark++)
{
if (f[i] ==
calc_follow[point1][lark])
{
chk = 1;
break;
}
}
if(chk == 0)
{
printf("%c, ", f[i]);
calc_follow[point1][point2++] =
f[i];
}
}
printf(" }\n\n");
km = m;
point1++;
}
}
void follow(char c)
{
int i, j;
if(production[0][0] == c) {
f[m++] = '$';
}
for(i = 0; i < 10; i++)
{
for(j = 2;j < 10; j++)
{
if(production[i][j] == c)
{
if(production[i][j+1] != '\0')
{
followfirst(production[i][j+1], i, (j+2));
}
if(production[i][j+1]=='\0'&& c!=production[i][0])
{
follow(production[i][0]);
}
}
}
}
}
void findfirst(char c, int q1, int q2)
{
int j;
if(!(isupper(c))) {
first[n++] = c;
}
for(j = 0; j < count; j++)
{
if(production[j][0] == c)
{
if(production[j][2] == '#')
{
if(production[q1][q2] == '\0')
first[n++] = '#';
else if(production[q1][q2] !=
'\0'
&& (q1 != 0 || q2 != 0))
{
findfirst(production[q1][q2], q1, (q2+1));
}
else
first[n++] = '#';
}
else if(!isupper(production[j][2]))
{
first[n++] = production[j][2];
}
else
{
findfirst(production[j][2], j,
3);
}
}
}
}
void followfirst(char c, int c1, int c2)
{
int k;
if(!(isupper(c)))
f[m++] = c;
else
{
int i = 0, j = 1;
for(i = 0; i < count; i++)
{
if(calc_first[i][0] == c)
break;
}
while(calc_first[i][j] != '!')
{
if(calc_first[i][j] != '#')
{
f[m++] = calc_first[i][j];
}
else
{
if(production[c1][c2] == '\0')
{
follow(production[c1][0]);
}
else
{
followfirst(production[c1][c2], c1, c2+1);
}
}
j++;
}
}
}
INPUT:
E -> TR
R -> +T R| #
T -> F Y
Y -> *F Y | #
F -> (E) | i
OUTPUT:
First(E)= { (, i, }
First(R)= { +, #, }
First(T)= { (, i, }
First(Y)= { *, #, }
First(F)= { (, i, }
Follow(E) = { $, ), }
Follow(R) = { $, ), }
Follow(T) = { +, $, ), }
Follow(Y) = { +, $, ), }
Follow(F) = { *, +, $, ), }
First(R)= { +, #, }
First(T)= { (, i, }
First(Y)= { *, #, }
First(F)= { (, i, }
Follow(E) = { $, ), }
Follow(R) = { $, ), }
Follow(T) = { +, $, ), }
Follow(Y) = { +, $, ), }
Follow(F) = { *, +, $, ), }
0 Comments
Post a Comment