Van Neuman Extractor

rand.rs

use std::fs::File;
use std::io::Read;
use std::mem::{transmute, size_of};

fn get_rand_int() -> u32 { 
    let mut b = [0;4];
    let mut f = File::open("/dev/random").expect("Coulnd't open");
    f.read(&mut b).expect("Coulnd't read");
    unsafe { transmute(b) }
}

fn flip_coin() -> bool { 
    let b = get_rand_int();
    (b % 8) == 0
}

fn extractor() -> bool { 
    let mut output = false;
    loop { 
        let a = flip_coin();
        let b = flip_coin();
        if a == b { 
            continue;
        } else { 
           output = a;
           break;
        }
    }
    output
}

fn run_expirement<T>(count : usize, f : T) -> f64 
    where T : Fn() -> bool {
    let mut heads = 0.0;
    for _ in 0..count { 
        if f() { heads += 1.0; }
    }
    heads / (count as f64)
}

fn main() -> () { 
    let args : Vec<_> = std::env::args().collect();
    let count : usize = args[1].parse().expect("Malformed args");
    let p1 = run_expirement(count, flip_coin);
    println!("Initial p = {}", p1);
    let p2 = run_expirement(count, extractor);
    println!("Extracted p = {}", p2);
}