Matrix determinant calculation by cofactor expansion by Rust

determinant.rs

use std::int::pow;
use std::rand;
use std::rand::Rng;

struct Matrix {
  p: ~[int],
       height: uint,
       width: uint
}

// 2D matrix with int elements
impl Matrix {
  fn at(&self, row: uint, col: uint) -> int {
    self.p[self.width * row + col]
  }

  fn dim(&self) -> (uint,uint) {
    (self.width,self.height)
  }

  fn is_square(&self) -> bool {
    self.width == self.height
  }
  
  fn det(&self) -> Option<int> {
    if self.is_square() {
      let (w,_) = self.dim();
      match w {
        2 =>
          match self.p {
            [a,b,c,d] => Some(a * d - b * c),
              _ => None
          },
        _ => Some({
          let mut s = 0i;
          for j in range(0,w) {
            match self.cofactor(0,j) {
              Some(cf) => s += self.at(0,j) * cf,
              _ => ()
            }
          }
          s
        })
      }
    } else {
      None
    }
  }
  fn cofactor(&self, i: uint, j: uint) -> Option<int> {
    let vs: ~[int] = self.p.iter().enumerate().filter(|&(k,_)| k / self.width != i && k % self.width != j)
        .map(|(_,&v)| v).collect();
    let rest = Matrix{p: vs,height: self.height-1, width: self.width-1};
    match rest.det() {
      Some(d) => {
        Some(pow(-1,i+j) * d)
      },
      _ => {
        None
      }
    }
  }
}

fn mkRnd(dim: uint) -> Matrix {
  let len = dim * dim;
  let mut rng = rand::task_rng();

  let vs = range(0, len).map(|_| rng.gen_range::<int>(-5,5)).collect();
  Matrix{p: vs, width: dim, height: dim}
}

fn main(){
  let m = Matrix{p: ~[1,2,3], width: 1, height: 3};
  let ms: ~[Matrix] = range(3,10).map(|n| mkRnd(n as uint)).collect();
  for m in ms.iter() {
    println!("{:?}",m.det());
  }

  println!("{:?}",m.dim());

}