unary minus doesn't negate string args

[myazinn]

JsonLogic:

{ "-": [ "4" ] }

As Java:

String expression = "{ \"-\": [ \"4\" ] }";
Map<String, Integer> data = new HashMap<>();
System.out.println(new JsonLogic().apply(expression, data));

Expected:
-4
Actual:
4.0

[verhas]

I tested it on the current HEAD on main branch and it returns -4.0

    @Test
    public void testBug47() throws JsonLogicException {
        String expression = "{ \"-\": [ \"4\" ] }";
        Map<String, Integer> data = new HashMap<>();
        Object result = new JsonLogic().apply(expression, data);
        Assert.assertEquals(result.getClass(),Double.class);
        Assert.assertTrue(((double)result) == -4.0);
    }