With today's C++ you can do these things without restriction - this means that this book has indeed some critical discrepancies with today's C++ compiler. In this case I was able to identify the issue, because I already learned and worked with operators and strings - but if I follow this book more down the road, it might lead me into thinking that some things are impossible/not yet implemented in c++ ...
Maybe it will, maybe it won't, but considering you've only just learnt about arrays, have you learnt about vectors? Have you learnt about linked lists? What design patterns have you learnt? They are all good theory, the implementation comes later. You'll be able to rewrite once you learn about new language features.
Or back to the car analogy. It doesn't matter if you learn about brakes on a 1982 car. Just because todays cars have ABS anti-lock brakes, you'll still learn enough to see what's happening.
The alternative is to wait for a brand-new C++17 Teach yourself book, but by the sound of you, you'd rather be doing something, making mistakes and learning by them.
Perhaps you're thinking that free things, things with no cost, also have no value, but that's silly in the Internet Age: but from a cost point of view, lets assume Bjarne Stroustrup's The C++ Programming Language, 4th Edition is $70 new. That only covers up to C++11. The 3rd edition is $5 second hand. Is the 4th edition worth the extra $65 to you now, or will the 3rd edition suffice until you reach a standard where you must know the new features, or the 5th edition comes out covering C++17.
Incidentally can you provide a reference / context for your quote "The two sides of a condition operator have to be the same type. You can only compare ints to ints and doubles to doubles. Unfortunately, at this point you can’t compare Strings at all! There is a way to compare Strings, but we won’t get to it for a couple of chapters.", because it just doesn't feel right? (C++ PL 3rd edition is from 2000, and BS is happily comparing strings)