Fix handling of QIRNot

src/qir/driver/QIRSQLVisitor.java

@@ -107,6 +107,10 @@ public class QIRSQLVisitor implements IQIRVisitor<String> {
         return "(" + qirNotEqual.getLeft().accept(this) + ") != (" + qirNotEqual.getRight().accept(this) + ")";
     }
 
+    public String visit(QIRNot qirNot) {
+        return "NOT (" + qirNot.getChild().accept(this) + ")";
+    }
+
     public String visit(QIRTable qirTable) {
         return qirTable.getTableName();
     }

src/qir/reduction/QIRGreedyReduceVisitor.java

@@ -134,6 +134,11 @@ public final class QIRGreedyReduceVisitor implements IQIRVisitor<QIRNode> {
         return new QIRNotEqual(qirNotEqual.getSourceSection(), qirNotEqual.getLeft().accept(this), qirNotEqual.getRight().accept(this));
     }
 
+    @Override
+    public QIRNode visit(QIRNot qirNot) {
+        return new QIRNot(qirNot.getSourceSection(), qirNot.getChild().accept(this));
+    }
+
     @Override
     public QIRNode visit(QIRVariable qirVariable) {
         if (env.containsKey(qirVariable.getId())) {

src/qir/util/IQIRVisitor.java

@@ -64,6 +64,8 @@ public interface IQIRVisitor<T> {
 
     public abstract T visit(QIRNotEqual qirNotEqual);
 
+    public abstract T visit(QIRNot qirNot);
+
     public abstract T visit(QIRTable qirTable);
 
     public default T visit(QIRList qirList) {

src/qir/util/QIRFreeVarsVisitor.java

@@ -142,6 +142,11 @@ public final class QIRFreeVarsVisitor implements IQIRVisitor<HashMap<String, QIR
         return qirNotEqual.getRight().accept(this);
     }
 
+    @Override
+    public HashMap<String, QIRVariable> visit(QIRNot qirNot) {
+        return qirNot.getChild().accept(this);
+    }
+
     @Override
     public HashMap<String, QIRVariable> visit(QIRTable qirTable) {
         return freeVariables;

src/qir/util/QIRPrintVisitor.java

@@ -109,6 +109,11 @@ public final class QIRPrintVisitor implements IQIRVisitor<String> {
         return "(" + qirNotEqual.getLeft().accept(this) + ") != (" + qirNotEqual.getRight().accept(this) + ")";
     }
 
+    @Override
+    public String visit(QIRNot qirNot) {
+        return "!(" + qirNot.getChild().accept(this) + ")";
+    }
+
     @Override
     public String visit(QIRTable qirTable) {
         return "Table(" + qirTable.getTableName() + ")";