What's the point of the NOT operator? [closed]

Question

Currently checking out C++ using this tutorial. It explains what the ! NOT operator is, kind of, but I don't think I fully understand why I'd ever want to use it. Can someone please explain?

Answer 1

The ! operator is useful if you want to check that a condition is not currently satisfied.

Imagine a function that tells you if a particular subsystem of your application was initialized and another function to initialize it:

bool subsystem_is_initialized();
void subsystem_initialize();

You could check that it was initialized and initialize it if it wasn't using the not operator.

if (!subsystem_is_initialized())
    subsystem_initialize();

For all practical purposes, it's a shorter way to compare a value to zero, with an explicit suggestion that the affected value is boolean. You don't absolutely need it, but then again, neither do you need multiplications (you can loop over an addition), additions (you can do it with binary logic), or most of binary logic (you can do pretty much anything with NANDs, I've been told, but I haven't researched it myself).

Also keep in mind that, like almost all other C++ operators, it can be overloaded by classes.

Answer 2

A language is not always (in fact as good as never) defined to have the minimal set of features but a set of features that useful. For example, if you had the following code:

if (!test_something())
  do_something();

You could also express this as

if (test_something()) {
} else
  do_something();

but it would be less easy to read. So, while logical negation can usually be expressed by other constructs of the C++ language, it helps readability to express negation explicitly to indicate your intent.