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[Beginner, C] If we can represent true/false with 1/0, why do we need the stdbool library and boolean variables? (programming.dev)
submitted 6 months ago* (last edited 6 months ago) by to c/learn_programming@programming.dev
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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

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[–] [S] 3 points 6 months ago (8 children)

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

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  • [–] 4 points 6 months ago (5 children)

    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".

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  • [–] 7 points 6 months ago (3 children)

    Except that a lot of the cstdlib functions return an int, where 0 == success, and negative numbers are falsy.

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  • [–] 2 points 6 months ago* (1 child)

    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.

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  • [–] 2 points 6 months ago

    Malloc return 0 is a failure, but open return 0 is success. It's just inconsistent, and it's definitely an age and context thing.

    Rust's Result api are a pretty great solution. Not sure what other options are out there though.

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  • [–] 4 points 6 months ago

    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 == variableB will 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.

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  • [–] 3 points 6 months ago (1 child)

    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.

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  • [–] 1 point 6 months ago* (last edited 6 months ago)

    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.

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