fix negative comparison

Author: sidhant92

src/main/java/com/github/sidhant92/boolparser/parser/antlr/BooleanFilterListener.java

@@ -62,7 +62,7 @@ public void exitArithmeticExpression(BooleanExpressionParser.ArithmeticExpressio
 
     @Override
     public void exitUnaryArithmeticExpression(BooleanExpressionParser.UnaryArithmeticExpressionContext ctx) {
-        final Node leafNode = !currentNodes.isEmpty() ? currentNodes.pop() : mapTypesExpressionContext(
+        final Node leafNode = !currentNodes.isEmpty() && currentNodes.peek() instanceof ArithmeticNode ? currentNodes.pop() : mapTypesExpressionContext(
                 (BooleanExpressionParser.TypesExpressionContext) ctx.exp);
         currentNodes.add(ArithmeticNode.builder().left(leafNode).operator(Operator.UNARY).build());
         super.enterUnaryArithmeticExpression(ctx);

src/test/java/com/github/sidhant92/boolparser/application/BooleanExpressionEvaluatorTest.java

@@ -587,6 +587,15 @@ public void testComparisonWithArithmeticFalseCondition1() {
         assertFalse(booleanOptional.get());
     }
 
+    @Test
+    public void testNegativeComparison() {
+        final Map<String, Object> data = new HashMap<>();
+        data.put("a", -6);
+        final Try<Boolean> resultOptional = booleanExpressionEvaluator.evaluate("a > -10 AND a < -2", data);
+        assertTrue(resultOptional.isSuccess());
+        assertEquals(resultOptional.get(), true);
+    }
+
     @Test
     public void testNullCheck() {
         final Map<String, Object> data = new HashMap<>();