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

1 files changed, 2 insertions, 0 deletions

diff --git a/src/prop/sat.h b/src/prop/sat.h
index e86443827..3f3166c14 100644
--- a/src/prop/sat.h
+++ b/src/prop/sat.h
@@ -236,6 +236,8 @@ public:
 
   void enqueueTheoryLiteral(const SatLiteral& l);
 
+  SatLiteral getNextDecisionRequest();
+
   bool theoryNeedCheck() const;
 
   void setCnfStream(CnfStream* cnfStream);