I saw one example
int x = 10;
int y = 5;
bool isGreater = x > y;
printf("%d", isGreater);
But I could write this
int x = 10;
int y = 5;
printf("%d", x > y);
I am a complete beginner and I have no real reason why I would or would not want to deal with boolean variables, but I want to understand their raison d’être.
Edit: typo city
I think there are several reasons. First, if you do it with an int, you’re probably using up 32bits per value. You’d need 1 but waste the other 31, they needlessly take up storage. (Edit: Though your bool will most likely take 8 bit anyways due to other things.) And then sometimes it’s nice to be expressive. So no one needs to remember if 1 is True or 0, or if True is greater than False, whether 2 or -1 map to True or False. And you end up in situations where either 2 equals 1, or True isn’t always equal True. Or you do weird things to handle values other than 0 and 1 in the operations. All of that can be avoided and the code gets more readable with specific types.
There’s nothing wrong with using ints, though. You just have to make sure the maths stays consistent.
Very nice point about the memory/storage usage! Also, I didn’t realize one can “map” other values as true/false than 1/0. But then again, I know very little at this moment. XD
Sure. As far as I remember in C, 0 is False. Every other number is True, you can use 1 or 42, doesn’t matter, they’re all “true”.
Except that a lot of the cstdlib functions return an int, where 0 == success, and negative numbers are falsy.
But I think one has to keep apart return codes that are signals to the OS and the end user, and 1/0 in a true/false context in conditional statements.
The way I make sense of it, is we sometimes return failure (i.e. from main). So 0 is no failure (aka success) and we can use the same thinking. The correct, expressive way to write it is probably use “EXIT_SUCCESS” and skip the ones and zeros. Pretty sure this comes from Unix. And with a lot of the other functions in cstdlib it’s the same way as using integers as booleans. For example a “malloc()” will either return your memory or a null pointer and the 0 is the special failure case.
But IMO the programming language shows its age and the context it was used in. More modern programming language design tends to be more strict with the types. Differentiate between interfacing with Unix stuff and other kinds of values. And we got more powerful concepts to deal with errors. So we don’t always have to abuse the zero to say we ended up in some special case.
Mallocreturn 0 is a failure, butopenreturn 0 is success. It’s just inconsistent, and it’s definitely an age and context thing.Rust’s
Resultapi are a pretty great solution. Not sure what other options are out there though.Okay, now… variableA = 1 (true) and variableB = 42 (true). Suppose we want to compare the values of them to see if they’re the same or different. A simple check of
if variableA == variableBwill return False, because while they’re both set to ‘true’, they’re set to different values of ‘true’. It could get problematic and become a way to introduce really weird bugs.Don’t be mislead by that comment. It implies that a boolean variable takes up 1 bit instead of 32. But most probably it will take 8 bits. You’re still “wasting” 7 bits instead of 31.
Good point. Yeah, my “probably” is doing a lot of heavy-lifting there. Thx, I’ve added a short sentence.) In reality we don’t really know the length of a bool nor an int type in C. Likely a bool is 1 Byte and an int is 4 Bytes. But that depends on the architecture and compiler. The bool it guaranteed to hold 0 and 1, so it must be at least 1 bit. But with how addressing works, it ends up being 8 bits (1 Byte) anyway. If we want to be more efficient than that, I believe we have to code something with bit fields. It’s a bit out of scope for a beginner, unless they do microcontroller stuff.
One project I worked with stored boolean values as bits in an 8-bit int, and then used binary math to read and write individual bits from that int, with each bit representing a distinct and independent boolean variable.
Really weird, complicated, and sounds kind of dumb … but it worked, and it was extremely memory-efficient.
Oh hey I do this in jwts too.
I need to encode a lot of permissions
Don’t ask
C++ actually does this ‘optimisation’ for
std::vector<bool>. I say ‘optimisation’ because it effectively trades time for space, which is usually the opposite of what you want - space is cheap, time usually isn’t. Sometimes it’s a good tradeoff though - it’s common in embedded development where you might only have a few kB of RAM.