this post was submitted on 22 Feb 2026
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Programmer Humor

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[–] Flipper@feddit.org 114 points 1 week ago* (last edited 1 week ago) (2 children)

Has the same vibes as anthropic creating a C compiler which passes 99% of compiler tests.

That last percent is really important. At least that last percent are some really specific edge cases right?

Description:
When compiling the following code with CCC using -std=c23:

bool is_even(int number) {
   return number % 2 == 0;
}

the compiler fails to compile due to booltrue, and false being unrecognized. The same code compiles correctly with GCC and Clang in C23 mode.

Source

Well fuck.

[–] PlexSheep@infosec.pub 27 points 1 week ago

If this wasn't 100% vibe coded, it would be pretty cool.

A c compiler written in rust, with a lot of basics supported, an automated test suite that compiles well known c projects. Sounds like a fun project or academic work.

[–] sus@programming.dev 4 points 1 week ago* (last edited 1 week ago)

The incredible thing is this is actually the result of an explicit design decision.

The compiler accepts most GCC flags. Unrecognized flags (e.g., architecture- specific -m flags, unknown -f flags) are silently ignored so ccc can serve as a drop-in GCC replacement in build systems.

They're so committed to vibing that they'd prefer if the compiler just does random shit to make it easier to shove it haphazardly into a build pipeline.

[–] SexualPolytope@lemmy.sdf.org 75 points 1 week ago

The error is ~1/log(x), for anyone interested.

[–] apex32@lemmy.world 63 points 1 week ago (3 children)
[–] savedbythezsh@sh.itjust.works 62 points 1 week ago (1 children)
[–] ulterno@programming.dev 11 points 1 week ago

infoView the source to see how I embedded the picture without copying it. The hover text had to be copied though.

[–] ulterno@programming.dev 17 points 1 week ago

infoView the source to see how I embedded the picture without copying it. The hover text had to be copied though.

[–] BradleyUffner@lemmy.world 31 points 1 week ago* (last edited 1 week ago) (2 children)

My favorite part of this is that they test it up to 99999 and we see that it fails for 99991, so that means somewhere in the test they actually implemented a properly working function.

[–] frank@sopuli.xyz 25 points 1 week ago (1 children)

No, it's always guessing false and 99991 is prime so it isn't right. This isn't the output of the program but the output of the program compared with a better (but probably not faster) isprime program

[–] BradleyUffner@lemmy.world 34 points 1 week ago (2 children)

Yes, that's what I said. They wrote another test program, with a correct implementation of IsPrime in order to test to make sure the pictured one produced the expected output.

[–] GalacticSushi@lemmy.blahaj.zone 42 points 1 week ago (2 children)

Plot twist: the test just checks to see if the input exists in a hardcoded list of all prime numbers under 100000.

[–] AI_toothbrush@lemmy.zip 20 points 1 week ago (1 children)

I mean people underestimate how usefull lookup tables are. A lookup table of primes for example is basically always just better except the one case where you are searching for primes which is more maths than computer programming anyways. The modern way is to abstract and reimplement everything when there are much cheaper and easier ways of doing it.

[–] ozymandias@sh.itjust.works 4 points 1 week ago (1 children)

more maths than computer programming anyways

Computer programming is a subset of maths and was invented by a mathematition, originally to solve a maths problem...

[–] AI_toothbrush@lemmy.zip 3 points 1 week ago (2 children)

Yeah but they slowly develop to be their own fields. You wouldnt argue that physics is math either. Or that chemistry could technically be called a very far branch of philosophy. Computer programing, physics, etc are the applied versions of math. You are no longer studying math, you are studying something else with the help of math. Not that it matters much, just makes distinguising between them easier. You can draw the line anywhere but people do generally have a somewhat shared idea of where that lies.

[–] ozymandias@sh.itjust.works 1 points 1 week ago (1 children)

Chemistry is a branch of alchemy

[–] MajorasTerribleFate@lemmy.zip 2 points 1 week ago (1 children)

I suppose, but only about insofar as the U.S. is a branch of the British Empire.

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[–] frank@sopuli.xyz 3 points 1 week ago (1 children)

Ah gotcha. Or a known list yeah

[–] draco_aeneus@mander.xyz 3 points 1 week ago

For prime numbers, since they're quite difficult to calculate and there's not that many of them, that's what's most common.

[–] anton@lemmy.blahaj.zone 9 points 1 week ago

That's a legitimate thing to do if you have a slow implementation that's easy to verify and a fast implementation that isn't.

[–] renzhexiangjiao@piefed.blahaj.zone 23 points 1 week ago* (last edited 1 week ago)

you can increase its accuracy by changing the parameter type to long

[–] JustARegularNerd@lemmy.dbzer0.com 16 points 1 week ago (3 children)

I'm struggling to follow the code here. I'm guessing it's C++ (which I'm very unfamiliar with)

bool is_prime(int x) {
    return false;
}

Wouldn't this just always return false regardless of x (which I presume is half the joke)? Why is it that when it's tested up to 99999, it has a roughly 95% success rate then?

[–] kraftpudding@lemmy.world 32 points 1 week ago (1 children)

I suppose because about 5% of numbers are actually prime numbers, so false is not the output an algorithm checking for prime numbers should return

[–] JustARegularNerd@lemmy.dbzer0.com 11 points 1 week ago (1 children)

Oh I'm with you, the tests are precalculated and expect a true to return on something like 99991, this function as expected returns false, which throws the test into a fail.

Thank you for that explanation

[–] Agent641@lemmy.world 3 points 1 week ago

And the natural distribution of primes gets smaller as integer length increases

[–] flamingo_pinyata@sopuli.xyz 29 points 1 week ago

That's the joke. Stochastic means probabilistic. And this "algorithm" gives the correct answer for the vast majority of inputs

[–] Hexarei@beehaw.org 4 points 1 week ago

Because only 5% of those numbers are prime

[–] lemmydividebyzero@reddthat.com 16 points 1 week ago

I have seen that algorithm before. It's also the implementation of an is_gay(Image i) algorithm with around 90% accuracy.

[–] Semi_Hemi_Demigod@lemmy.world 14 points 1 week ago* (last edited 1 week ago) (3 children)

If you scaled it based on the size of the integer you could get that up to 99.9% test accuracy. Like if it's less than 10 give it 50% odds of returning false, if it's under 50 give it 10% odds, otherwise return false.

[–] LodeMike@lemmy.today 4 points 1 week ago (2 children)

That would make it less accurate. It's much more likely to return true on not a prime than a prime

[–] Semi_Hemi_Demigod@lemmy.world 2 points 1 week ago

Code proof or it didn't happen.

Extra credit for doing it in Ruby

[–] themusicman@lemmy.world 2 points 1 week ago (1 children)

Correct. Not are why people are upvoting. If 10% of numbers are prime in a range, and you always guess false, you get 90% right. If you randomly guess true 10% of the time, you get ~80% right.

[–] LodeMike@lemmy.today 1 points 1 week ago (1 children)

More random means more towards 50% correctness.

[–] ptu@sopuli.xyz 3 points 1 week ago

And 2,3,5,7 are primes of the first numbers, making always false 60% correct and random chance 50%

[–] Jayjader@jlai.lu 4 points 1 week ago

Now you're thinking with ~~portals~~ primes!

[–] JackbyDev@programming.dev 1 points 1 week ago* (last edited 1 week ago)

Makes me wonder where the actual break even would be. Like how long does making one random number take versus sins lookups. Fuck it, do it in parallel. Fastest wins.

[–] red_tomato@lemmy.world 10 points 1 week ago (1 children)

It has actually 100% accuracy

[–] JustJack23@slrpnk.net 12 points 1 week ago (1 children)
[–] clav64@lemmy.world 5 points 1 week ago

Can we just call the algorithm sex panther and move on?

[–] Kekzkrieger@feddit.org 9 points 1 week ago

If you think this is bad and not nearly enough accuracy to be called correct, AI is much worse than this.

It's not just wrong a lot of times or hallucinates but you can't pinpoint why or how it produces the result and if you keep putting the same data in, the output may still vary.

[–] Prime@lemmy.sdf.org 7 points 1 week ago

100% of the time, baby =)

[–] zbyte64@awful.systems 5 points 1 week ago

Pssh, mine uses a random number generator for odd numbers to return true 4% of the time to achieve higher accuracy and a bettor LLM metaphor

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