From f00060b2bdbbb0a3b609a40f1c5e61d7d30d5841 Mon Sep 17 00:00:00 2001
From: "Sven M. Hallberg" <pesco@khjk.org>
Date: Wed, 8 May 2013 16:12:34 +0200
Subject: [PATCH] add (untested) predict set computation
---
src/backends/ll.c | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)
diff --git a/src/backends/ll.c b/src/backends/ll.c
index 591bc2dc..176490d4 100644
--- a/src/backends/ll.c
+++ b/src/backends/ll.c
@@ -25,7 +25,21 @@ unsigned int h_ll_lookup(const HLLTable *table, unsigned int nonterminal, uint8_
}
#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)
{
--
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