Added OutputChannel::propagateAsDecision() functionality, allowing a theory

to request a decision on a literal.  All these theory requests are kept in a
context-dependent queue and serviced in order when the SAT solver goes to make a
decision.  Requests that don't have a SAT literal give an assert-fail.  Requests
for literals that already have an assignment are silently ignored.

Since the queue is CD, requests can actually be serviced more than once (e.g., if
a request is made at DL 5, but not serviced until DL 10, and later, a conflict
backtracks to level 7, the request may be serviced again).

Performance impact: none to negligible for theories that don't use it
  See http://church.cims.nyu.edu/regress-results/compare_jobs.php?job_id=3620&reference_id=3614&mode=&category=&p=0

2 files changed, 8 insertions, 0 deletions

diff --git a/test/unit/theory/theory_black.h b/test/unit/theory/theory_black.h
index 60e090d16..76385219d 100644
--- a/test/unit/theory/theory_black.h
+++ b/test/unit/theory/theory_black.h
@@ -62,6 +62,11 @@ public:
     push(PROPAGATE, n);
   }
 
+  void propagateAsDecision(TNode n)
+    throw(AssertionException) {
+    // ignore
+  }
+
   LemmaStatus lemma(TNode n, bool removable)
     throw(AssertionException) {
     push(LEMMA, n);
diff --git a/test/unit/theory/theory_engine_white.h b/test/unit/theory/theory_engine_white.h
index 2363e4906..8d7bc9c72 100644
--- a/test/unit/theory/theory_engine_white.h
+++ b/test/unit/theory/theory_engine_white.h
@@ -54,6 +54,9 @@ class FakeOutputChannel : public OutputChannel {
   void propagate(TNode n) throw(AssertionException) {
     Unimplemented();
   }
+  void propagateAsDecision(TNode n) throw(AssertionException) {
+    Unimplemented();
+  }
   LemmaStatus lemma(TNode n, bool removable) throw(AssertionException) {
     Unimplemented();
   }