\ud83d\udcdd If S is start \u2192 FOLLOW(S) = { $ }<\/code><\/p><\/blockquote>\n
\n\ud83d\udd39 Rule 2: A \u2192 \u03b1B\u03b2 Rule (Non-terminal followed by symbols)<\/strong><\/h3>\nIf there is a production like:
\nA \u2192 \u03b1 B \u03b2<\/code><\/p>\n\u27a1 Then, everything in FIRST(\u03b2)<\/strong> (except \u03b5) is added to FOLLOW(B)<\/strong>.<\/p>\n\u2705 FOLLOW(B) += FIRST(\u03b2) \u2013 { \u03b5 }<\/strong><\/p><\/blockquote>\n
\n\ud83d\udd39 Rule 3: A \u2192 \u03b1B or A \u2192 \u03b1B\u03b2 where \u03b2 \u21d2 \u03b5 (Nullable)<\/strong><\/h3>\nIf B is at the end<\/strong>, or \u03b2 \u21d2 \u03b5<\/strong>, then
\nFOLLOW(B) += FOLLOW(A)<\/strong><\/p>\n\u2705 This is called “FOLLOW through FOLLOW”<\/strong>
\n(when nothing follows B, or what follows is nullable)<\/p><\/blockquote>\n
\n\ud83d\udd39 Rule 4: Keep Applying Until Stable<\/strong><\/h3>\nApply all above rules iteratively<\/strong> until no new symbols are added.<\/p>\n
\n\ud83e\uddea Example Using Shortcut:<\/strong><\/h2>\nLet\u2019s take a simple grammar:<\/p>\n
S \u2192 A B \nA \u2192 a | \u03b5 \nB \u2192 b\n<\/code><\/pre>\n
\n\ud83d\udd0d Step-by-Step:<\/h3>\n\u27a4 FIRST Sets:<\/h4>\n\n- FIRST(A) = { a, \u03b5 }<\/li>\n
- FIRST(B) = { b }<\/li>\n<\/ul>\n
\n\ud83d\udd0e FOLLOW(S):<\/h3>\n\n- S is start symbol \u2192 FOLLOW(S) = {
$<\/code> }<\/li>\n<\/ul>\n
\n\ud83d\udd0e FOLLOW(A):<\/h3>\n
S \u2192 A B
\n\u2192 A is followed by B \u2192 so:<\/p>\n
\u2705 FOLLOW(A) += FIRST(B) = { b }<\/p>\n
\n\ud83d\udd0e FOLLOW(B):<\/h3>\n
S \u2192 A B \u2192 B is at end \u2192 FOLLOW(B) += FOLLOW(S) = { $<\/code> }<\/p>\n
\n\u2705 Final FOLLOW Sets:<\/h3>\n
\n\n\n| Non-terminal<\/th>\n | FOLLOW<\/th>\n<\/tr>\n<\/thead>\n |
\n\n| S<\/td>\n | { $<\/code> }<\/td>\n<\/tr>\n\n| A<\/td>\n | { b }<\/td>\n<\/tr>\n | \n| B<\/td>\n | { $<\/code> }<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\n\ud83d\udca1 Pro Tips:<\/strong><\/h2>\n | |