pub fn extract(&self) -> (Vec<usize>, Vec<usize>, ComplexMatrix, ComplexMatrix) {
        (
            self.p.clone(),
            self.q.clone(),
            self.l.clone(),
            self.u.clone(),
        )
    }
Extract PQLU

# Usage
```rust
extern crate peroxide;
use peroxide::fuga::*;

let a = cmatrix(vec![C64::new(1f64, 1f64),
C64::new(2f64, 2f64),
C64::new(3f64, 3f64),
C64::new(4f64, 4f64)],
2, 2, Row
);
let pqlu = a.lu();
let (p, q, l, u) = pqlu.extract();
// p, q are permutations
// l, u are matrices
println!("{}", l); // lower triangular
println!("{}", u); // upper triangular
```
src/complex/matrix.rs