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add (untested) predict set computation

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This commit is contained in:
Sven M. Hallberg 2013-05-08 16:12:34 +02:00
parent 2943cfdfdd
commit f00060b2bd
1 changed files with 15 additions and 1 deletions
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16
src/backends/ll.c
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@ -25,7 +25,21 @@ unsigned int h_ll_lookup(const HLLTable *table, unsigned int nonterminal, uint8_
} }
#endif #endif
// XXX predict_set /* Compute the predict set of production "A -> rhs". */
HHashSet *h_predict(HCFGrammar *g, const HCFChoice *A, const HCFSequence *rhs)
{
// predict(A -> rhs) = first(rhs) u follow(A) if "" can be derived from rhs
// predict(A -> rhs) = first(rhs) otherwise
HHashSet *first_rhs = h_first_sequence(g, rhs->items);
if(h_sequence_derives_epsilon(g, rhs->items)) {
HHashSet *ret = h_hashset_new(g->arena, h_eq_ptr, h_hash_ptr);
h_hashset_put_all(ret, first_rhs);
h_hashset_put_all(ret, h_follow(g, A));
return ret;
} else {
return first_rhs;
}
}
int h_ll_compile(HAllocator* mm__, const HParser* parser, const void* params) int h_ll_compile(HAllocator* mm__, const HParser* parser, const void* params)
{ {