fn sign(&self) -> f64 {
        let l = self.len();
        let mut v = self.clone();
        let mut sgn = 1f64;

        for i in 0..(l - 1) {
            for j in 0..(l - 1 - i) {
                if v[j] > v[j + 1] {
                    sgn *= -1f64;
                    let (a, b) = (v[j], v[j + 1]);
                    v[j] = b;
                    v[j + 1] = a;
                }
            }
        }
        sgn
    }
Sign of Permutation

# Examples
```
#[macro_use]
extern crate peroxide;
use peroxide::fuga::*;

fn main() {
let a = c!(1,0,2);
let b = c!(1,2,0);
let c = c!(0,1,2);

assert_eq!((a.sign(), b.sign(), c.sign()), (-1f64, 1f64, 1f64));
}
```
src/structure/vector.rs