tri-sur.rs

#![feature(rustc_private)]
extern crate rand;

use rand::Rng;
use std::ops::{Add, Sub};

#[derive(Clone, Copy, Debug)]
struct Pt {
    x : f64,
    y : f64,
}

impl Pt {
    fn new(x : f64, y : f64) -> Self {
        Pt{x:x, y:y}
    }
    fn rand(rng : &mut rand::ThreadRng) -> Self {
        Self::new(rng.gen(), rng.gen())
    }

    fn dot(&self, other : &Self) -> f64 {
        self.x * other.x + self.y * other.y
    }
    fn normsq(&self) -> f64 {
        self.dot(self)
    }
}
impl Add for Pt {
    type Output = Self;
    fn add(self, other : Self) -> Self {
        Self::new(self.x + other.x, self.y + other.y)
    }
}
impl Sub for Pt {
    type Output = Self;
    fn sub(self, other : Self) -> Self {
        Self::new(self.x - other.x, self.y - other.y)
    }
}

fn tri_surface(a : Pt, b : Pt, c : Pt) -> f64 {
    let v1 = c-a;
    let v2 = b-a;
    (v1.normsq() * v2.normsq() - v1.dot(&v2) * v1.dot(&v2)).sqrt() / 2.0
}

fn main() {
    let mut rng = rand::thread_rng();
    let mut sum = 0.0;
    let tries = 1000000;
    for _ in 1..tries {
        let (a, b, c) = (Pt::rand(&mut rng), Pt::rand(&mut rng), Pt::rand(&mut rng));
        sum += tri_surface(a, b, c);
    }
    println!("{}", sum / tries as f64);
}