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Comment by riverlong | Hacker News Reader

Where in C is 0 truthy (or 1 falsy)?

strcmp,memcmp,etc. return 0 for equality, maybe you'd count that? But it's not really indicating "true", more "no difference".

main() returns 0 for success, but I expect that is owed more to Unix.

A lot of (e.g. Linux) system calls return 0 for success and an error value on error, but again that's more down to Unix than C.

I wouldn't count strcmp, etc. It returns < 0 if str1 is shorter and > 0 if str1 is longer. Returning 0 means there is 0 difference. That's not a True/False.

"0" is not a "truthy" exit code for a system call, it rather denotes the absence of an error.

In my view, a value X being "truthy" means that `bool(X)` evaluates to TRUE, or `if(X)` gets executed.

I think it’s where many functions return 0 when they are successful.

maybe cause there's only one way to succeed and many ways to error. 0 success and 1..N are error codes.

what is a reasonable alternative?

(this isnt the same as 0 false and 1 true)

Ok, but:

     success vs. fail

is different than:

     true vs. false

They're both binary, but only one is boolean.

https://pubs.opengroup.org/onlinepubs/009695399/basedefs/std...

I think those go in the opposite direction.

Well, unix, as in exit codes.

Yeah, exit codes aren't what I'm talking about here.

In Hoon/Nock, `if(0)` literally gets interpreted as True. That's insane.

In lambda calculus, true and false are conventionally represented as functions

    lambda x. lambda y. x

and

    lambda x. lambda y. y

so that "if b then x else y" is represented by "b x y". When identifying booleans with bits, it seems natural to write this as "bit x_0 x_1" rather than "bit x_1 x_0" where the arguments seem to be in the wrong order.

This is one possible justification for identifying true with 0 and false with 1.

It's not insane, just dissimilar to what you're used to.

Okay, it's not insane, it just breaks from a convention followed by practically every programming language (and every logic / engineering / computing course) where integers can be interpreted as booleans. And that might be okay if there's a good reason, but the reasons given are pretty awful:

https://news.ycombinator.com/item?id=11852434

Ruby is one popular example of a language with a truthy zero. This is to allow the use of truthiness to detect the presence of a value (as long as the value isn't false), even if the value is zero. Say I wanted to allow an environment variable to override a value in my code. I could do something like this:

    a = ENV['A']&.to_i || 1

and then run the program with A=0 to set a to 0.

Perl has this too. The string "0 but true" is truthy, but is 0 as a numeric value.

(Any string starting with 0 that doesn't evaluate to a different number also works - but "0 but true" is specifically exempt from causing warnings).

DBI uses "0E0" instead, which I guess more reliably evaluates to 0 outside Perl, and still doesn't cause warnings.

That approach is not unreasonable per se. But 1 being false is much harder to rationalize.

Dissimilarity for no good reason is, well, maybe not insanity but plain old dumb. Unless we're talking fashion not software projects, hence the "vanity" classification.

i don't really see why. if anything is insane, it's interpreting a number as true or false. but if you're doing that anyway, then you pick a number for false, or you pick a number for true. 0 is a natural number to pick for whichever truth value, because it's the base case of the natural numbers.

it's unconventional, but no more insane than 0 = false, which, again, _is_ insane, but conventional.

i'm not bothered either way

Using 0 as false and 1 as true has the benefit that + (mod 2) becomes xor and * becomes and.

(or, if instead of mod 2, you use min(1,a + b) to keep things in the set, then + becomes or )

To use 0 as true and 1 as false, you don't get nice things like this. It's not nice.

Well.. I guess * becomes or. But, + (mod 2) becomes, uh, xnor , and (min(1,a+b)) becomes, and...

ok well I guess that's not as bad as I thought.

Still a bad decision imo though.

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