anchor.diff:        expect(evaluator.parse('2 + 3 * 4').value, closeTo(14, epsilon));
         expect(evaluator.parse('6 / 3 + 4').value, closeTo(6, epsilon));
         expect(evaluator.parse('2 + 6 / 2').value, closeTo(5, epsilon));
  +    });
  +    test('priority parse', () {
  +      expect(parser.parse('2 * 3 + 4').value, [[2.0, '*', 3.0], '+', 4.0]);
  +      expect(parser.parse('2 + 3 * 4').value, [2.0, '+', [3.0, '*', 4.0]]);
       });
       test('postfix add', () {
         expect(evaluator.parse('0++').value, closeTo(1, epsilon));
  
positive.code:       expect(evaluator.parse('1 * 2 * 3 * 4').value, closeTo(24, epsilon));
        expect(evaluator.parse('1 * 2 * 3 * 4 * 5').value, closeTo(120, epsilon));
      });
      test('div', () {
        expect(evaluator.parse('12 / 3').value, closeTo(4, epsilon));
        expect(evaluator.parse('-16 / -4').value, closeTo(4, epsilon));
  
negative.code:       expect(evaluator.parse('34.7').value, closeTo(34.7, epsilon));
        expect(evaluator.parse('56.78').value, closeTo(56.78, epsilon));
      });
      test('number negative', () {
        expect(evaluator.parse('-1').value, closeTo(-1, epsilon));
        expect(evaluator.parse('-1.2').value, closeTo(-1.2, epsilon));
      });
      test('number parse', () {
        expect(parser.parse('0').value, 0);
        expect(parser.parse('-1').value, ['-', 1]);
      });
      test('add', () {
        expect(evaluator.parse('1 + 2').value, closeTo(3, epsilon));
  