calculation for standard deviation seems wrong

[flameoftheforest]

fn main() {
  let v = vec![1.0, 1.0, 2.0];
  let mut stdev = StDev::new(3, &v[0]).unwrap();
  stdev.next(&v[1]);
  assert_eq!(stdev.next(&v[2]), 0.4714045207910317);
}

assert failed.

[amv-dev]

1. You can't use strict comparison with float values.
2. The right value is 0.577350269189626. yata uses corrected sample standard deviation.

[flameoftheforest]

thanks for reply. i understand now.