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always put end_token in the start symbol's follow set

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Sven M. Hallberg 2013-05-12 16:51:35 +02:00
parent f33390a510
commit b488e5485f
1 changed files with 5 additions and 0 deletions
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5
src/cfgrammar.c
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@ -258,6 +258,7 @@ HHashSet *h_follow(HCFGrammar *g, const HCFChoice *x)
{ {
// consider all occurances of X in g // consider all occurances of X in g
// the follow set of X is the union of: // the follow set of X is the union of:
// {$} if X is the start symbol
// given a production "A -> alpha X tail": // given a production "A -> alpha X tail":
// if tail derives epsilon: // if tail derives epsilon:
// first(tail) u follow(A) // first(tail) u follow(A)
@ -275,6 +276,10 @@ HHashSet *h_follow(HCFGrammar *g, const HCFChoice *x)
assert(ret != NULL); assert(ret != NULL);
h_hashtable_put(g->follow, x, ret); h_hashtable_put(g->follow, x, ret);
// if X is the start symbol, the end token is in its follow set
if(x == g->start)
h_hashset_put(ret, (void *)end_token);
// iterate over g->nts // iterate over g->nts
size_t i; size_t i;
HHashTableEntry *hte; HHashTableEntry *hte;