extern crate num;
use num::traits::{RefNum, Num};


/// cross product of vectors AB and AC
pub fn cross2d<T>(a: &[T;2], b: &[T;2], c: &[T;2]) -> T where
	for<'a> &'a T: RefNum<T>,
    T: Num {

	return (&b[0]-&a[0]) * (&c[1]-&a[1]) - (&b[1]-&a[1]) * (&c[0]-&a[0]);
}

/// cross product of vectors AB and AC
pub fn cross<'a, 'b, 'c>(a: &'a [i32;2], b: &'b [i32;2], c: &'c [i32;2]) -> i32 {

	return (&b[0]-&a[0]) * (&c[1]-&a[1]) - (&b[1]-&a[1]) * (&c[0]-&a[0]);
}

pub fn main() {
    let x = [0i32, 0i32];
    let y = [1i32, 0i32];
    let z = [0i32, 1i32];

    println!("{}", cross2d(&x, &y, &z));
    println!("{}", cross(&x, &y, &z));
}