use acyclic iteration when projecting onto query vars

2019-02-22 17:48:49 -07:00
parent f41b5f465e
commit 6ba47b6b08
6 changed files with 30 additions and 14 deletions
--- a/src/prolog/machine/system_calls.rs
+++ b/src/prolog/machine/system_calls.rs
@@ -743,6 +743,12 @@ impl MachineState {
                let a2 = self[temp_v!(2)].clone();
                self.unify(a2, outcome);
            },
+            &SystemClauseType::TruncateLiftedHeapTo =>
+                match self.store(self.deref(self[temp_v!(1)].clone())) {
+                    Addr::Con(Constant::Usize(lh_offset)) =>
+                        self.lifted_heap.truncate(lh_offset),
+                    _ => self.fail = true
+                },
            &SystemClauseType::UnwindStack => self.unwind_stack(),
            &SystemClauseType::WriteTerm => {
                let addr = self[temp_v!(1)].clone();