anchor.diff:        expect(evaluator.parse('100 / 2 / 2 / 5').value, closeTo(5, epsilon));
         expect(evaluator.parse('100 / 2 / 2 / 5 / 5').value, closeTo(1, epsilon));
       });
  +    test('mul parse', () {
  +      expect(parser.parse('1 / 2 / 3').value, [[1, '/', 2], '/', 3]);
  +    });
       test('pow', () {
         expect(evaluator.parse('2 ^ 3').value, closeTo(8, epsilon));
         expect(evaluator.parse('-2 ^ 3').value, closeTo(-8, epsilon));
  
positive.code:       expect(evaluator.parse('34.7').value, closeTo(34.7, epsilon));
        expect(evaluator.parse('56.78').value, closeTo(56.78, epsilon));
      });
      test('negative number', () {
        expect(evaluator.parse('-1').value, closeTo(-1, epsilon));
        expect(evaluator.parse('-1.2').value, closeTo(-1.2, epsilon));
      });
      test('add', () {
        expect(evaluator.parse('1 + 2').value, closeTo(3, epsilon));
  
negative.code:       expect(evaluator.parse('1 - 2 - 3 - 4').value, closeTo(-8, epsilon));
        expect(evaluator.parse('1 - 2 - 3 - 4 - 5').value, closeTo(-13, epsilon));
      });
      test('sub parse', () {
        expect(parser.parse('1 - 2 - 3').value, [[1, '-', 2], '-', 3]);
      });
      test('mul', () {
        expect(evaluator.parse('2 * 3').value, closeTo(6, epsilon));
        expect(evaluator.parse('2 * -4').value, closeTo(-8, epsilon));
  