Monte carlo pi estimation in rust

main.rs

extern crate rand;

use rand::{thread_rng, Rng};
use std::f64;

struct Point {
    pub x: f64,
    pub y: f64
}

fn point_in_unit_circle(pt: Point) -> bool {
    let centre = 0.0;
    let dist = f64::sqrt(pt.x*pt.x+pt.y*pt.y);
    dist < 1.0
}


fn estimate_pi(samples: i32) -> f64 {
    let mut in_circle:i32 = 0;
    let mut rng = thread_rng();
    for _i in 0..samples {
        let s_x: f64 = rng.gen_range(-1.00, 1.00);
        let s_y: f64 = rng.gen_range(-1.00, 1.00);
        let point = Point{x:s_x, y:s_y};
        if point_in_unit_circle(point) {
            in_circle += 1;
        }
    }

    return ((f64::from(in_circle))/(f64::from(samples)))*4.0;
}

fn main() {
    println!("Pi tho");

    for pw in 0..8 {
        println!("10^{} samples: pi={}", pw, estimate_pi(i32::pow(10, pw)));
    }
}

e.g.

10^0 samples: pi=4
10^1 samples: pi=1.6
10^2 samples: pi=3.28
10^3 samples: pi=3.06
10^4 samples: pi=3.1656
10^5 samples: pi=3.14236
10^6 samples: pi=3.142372
10^7 samples: pi=3.1408304