anchor.diff:        expect(exec('(cdr! (cons 1 2) 3)'), new Cons(1, 3));
       });
     });
  -
   }
positive.code:       expect(exec('(and true false)'), isFalse);
        expect(exec('(and false true)'), isFalse);
        expect(exec('(and false false)'), isFalse);
      });
      test('And (lazyness)', () {
        expect(exec('(and false (set! a true)) a'), isNull);
  
negative.code:       expect(exec('(or true false)'), isTrue);
        expect(exec('(or false true)'), isTrue);
        expect(exec('(or false false)'), isFalse);
        expect(exec('(or true true true)'), isTrue);
        expect(exec('(or true true false)'), isTrue);
        expect(exec('(or true false true)'), isTrue);
        expect(exec('(or true false false)'), isTrue);
        expect(exec('(or false true true)'), isTrue);
        expect(exec('(or false true false)'), isTrue);
        expect(exec('(or false false true)'), isTrue);
        expect(exec('(or false false false)'), isFalse);
      });
      test('Or (lazyness)', () {
        expect(exec('(or false (set! a true)) a'), isTrue);
  