Improve and slightly change hex formatting

tests/tivars.py

@@ -138,6 +138,11 @@ def test_truthiness(self):
         test_program.clear()
         self.assertEqual(bool(test_program), True)
 
+    def test_hex(self):
+        test_program = TIEntry.open("tests/data/var/Program.8xp")
+        self.assertEqual(f"{test_program}", "setDate(1")
+        self.assertEqual(f"{test_program:-2X:}", "0300:EF00:31")
+
 
 class TokenizationTests(unittest.TestCase):
     def test_load_from_file(self):

tivars/var.py

@@ -431,19 +431,24 @@ def __format__(self, format_spec: str) -> str:
         :return: A string representation of this entry
         """
 
-        if match := re.fullmatch(r"(?P<sep>\D)?(?P<width>\d+)?x", format_spec):
+        if match := re.fullmatch(r"(?P<width>[+-]?\d+)?(?P<case>[xX])(?P<sep>\D)?", format_spec):
             match match["sep"], match["width"]:
                 case None, None:
-                    return self.calc_data.hex()
+                    string = self.calc_data.hex()
 
                 case sep, None:
-                    return self.calc_data.hex(sep)
+                    string = self.calc_data.hex(sep)
 
                 case None, width:
-                    return self.calc_data.hex(" ", int(width))
+                    string = self.calc_data.hex(" ", int(width))
 
                 case sep, width:
-                    return self.calc_data.hex(sep, int(width))
+                    string = self.calc_data.hex(sep, int(width))
+
+            return string if match["case"] == "x" else string.upper()
+
+        elif not format_spec:
+            return super().__str__()
 
         else:
             raise TypeError(f"unsupported format string passed to {type(self)}.__format__")