fix duplicate_term bug

src/prolog/ast.rs

@@ -338,6 +338,7 @@ pub enum QueryTerm {
     Catch(Vec<Box<Term>>),    
     Cut,
     Display(Vec<Box<Term>>),
+    DuplicateTerm(Vec<Box<Term>>),
     Functor(Vec<Box<Term>>),
     Inlined(InlinedQueryTerm),
     Is(Vec<Box<Term>>),
@@ -350,8 +351,9 @@ impl QueryTerm {
         match self {
             &QueryTerm::Arg(_) => 3,
             &QueryTerm::Catch(_) => 3,
-            &QueryTerm::Throw(_) => 1,
+            &QueryTerm::Throw(_) => 1,            
             &QueryTerm::Display(_) => 1,
+            &QueryTerm::DuplicateTerm(_) => 2,
             &QueryTerm::Functor(_) => 3,
             &QueryTerm::Inlined(ref term) => term.arity(),
             &QueryTerm::Is(_) => 2,
@@ -720,7 +722,6 @@ pub enum ArithmeticInstruction {
 pub enum BuiltInInstruction {
     CleanUpBlock,
     CompareNumber(CompareNumberQT, ArithmeticTerm, ArithmeticTerm),
-    DuplicateTerm,
     EraseBall,
     Fail,
     GetArg,
@@ -751,6 +752,8 @@ pub enum ControlInstruction {
     Deallocate,
     DisplayCall,
     DisplayExecute,
+    DuplicateTermCall,
+    DuplicateTermExecute,
     Execute(Rc<Atom>, usize),
     ExecuteN(usize),
     FunctorCall,
@@ -773,6 +776,8 @@ impl ControlInstruction {
             &ControlInstruction::CatchExecute => true,
             &ControlInstruction::DisplayCall => true,
             &ControlInstruction::DisplayExecute => true,
+            &ControlInstruction::DuplicateTermCall => true,
+            &ControlInstruction::DuplicateTermExecute => true,
             &ControlInstruction::Execute(_, _)  => true,
             &ControlInstruction::CallN(_) => true,
             &ControlInstruction::ExecuteN(_) => true,