add display predicate

src/prolog/ast.rs

@@ -335,8 +335,9 @@ pub enum CompareNumberQT {
 pub enum QueryTerm {
     Arg(Vec<Box<Term>>),
     CallN(Vec<Box<Term>>),
-    Catch(Vec<Box<Term>>),
+    Catch(Vec<Box<Term>>),    
     Cut,
+    Display(Vec<Box<Term>>),
     Functor(Vec<Box<Term>>),
     Inlined(InlinedQueryTerm),
     Is(Vec<Box<Term>>),
@@ -350,6 +351,7 @@ impl QueryTerm {
             &QueryTerm::Arg(_) => 3,
             &QueryTerm::Catch(_) => 3,
             &QueryTerm::Throw(_) => 1,
+            &QueryTerm::Display(_) => 1,
             &QueryTerm::Functor(_) => 3,
             &QueryTerm::Inlined(ref term) => term.arity(),
             &QueryTerm::Is(_) => 2,
@@ -747,6 +749,8 @@ pub enum ControlInstruction {
     CatchCall,
     CatchExecute,
     Deallocate,
+    DisplayCall,
+    DisplayExecute,
     Execute(Rc<Atom>, usize),
     ExecuteN(usize),
     FunctorCall,
@@ -767,6 +771,8 @@ impl ControlInstruction {
             &ControlInstruction::Call(_, _, _)  => true,
             &ControlInstruction::CatchCall => true,
             &ControlInstruction::CatchExecute => true,
+            &ControlInstruction::DisplayCall => true,
+            &ControlInstruction::DisplayExecute => true,
             &ControlInstruction::Execute(_, _)  => true,
             &ControlInstruction::CallN(_) => true,
             &ControlInstruction::ExecuteN(_) => true,