On your test-run factorion replied on 6.631537423e-34! with Factorial of 6.631537423 × 10-34 is approximately 1, before that it was replying with Factorial of 0.000000000000000000000000663154 is approximately 0,999999999999999999999999617217.

https://www.reddit.com/r/testingground4bots/comments/1rabfbh/comment/o77a0e8/

The before reply was more precise

Ok investigating this I found, that the true result is 9.999999999999999999999999999999996172172717063657224823672597116605474397837555828144330523967376628717255627642017055031081750434013261087338778618778539329115394750197229780734699344408893837837414084874090262554352460558789098273872863113806646310596473029774819683214882891955307493169687938970352854185035e-1 not 0.999999999999999999999999617217. That's a lot more 9s in reality (more than 30).

Even though I confirmed we now do better (as more correct), I wanna figure out why it was wrong previously.

Checked on master now, and can't reproduce that response, just get 0.1. What options (consts like float_precision) did you use?

Checked on master now, and can't reproduce that response, just get 0.1. What options (consts like float_precision) did you use?

I needed a while to reproduce, but it happens to me only if the language is NOT en.

Example-test:

#[test]
fn teststuff() {
    let consts = Consts::default();
    let comment = Comment::new(
        "6.631537423e-34! ",
        (),
        Commands::TERMIAL,
        MAX_LENGTH,
        "de",
    )
        .extract(&consts)
        .calc(&consts);

    let reply = comment.get_reply(&consts);
    assert_eq!(
        reply,
        "Fakultät von 0,000000000000000000000000663154 ist ungefähr 0,999999999999999999999999617217 \n\n\n*^(Dieser Kommentar wurde automatisch geschrieben | [Quelltext](http://f.r0.fyi))*"
    );
}

for en the test would fail, for en the reply would have been Factorial of 0 is approximately 0.1 \n\n\n*^(This action was performed by a bot | [Source code](http://f.r0.fyi))* as you stated.

Oh, It's not doing the same calculation at all. Since the decimal separator is ',' and not '.' the latter is simply ignored.

So on en we calculate the factorial of 6.631537423e-34, but on ru and de, we calculate the factorial of 6631537423e-34.

I am unsure on what should be done. To "fix" this we would have to somehow find, when it is not used as a separator, specifying some pattern of separators per locale (char and interval?) and then? Treat it as a decimal separator or give an error or something?

Ohh, right! That was my bad!
Its basically 0.0000000000000000000000000000000006631537423 vs 0.0000000000000000000000006631537423.

This is whole other issue as it appears. We would need a heuristic approach that makes assumptions about the separator.

I can merge the PR later in the evening, as it seems to work as intended to me.