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// Copyright 2019 Developers of the Rand project.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use num_traits::Float;
use crate::{uniform::SampleUniform, Distribution, Uniform};
use rand::Rng;
/// Samples uniformly from the unit disc in two dimensions.
///
/// Implemented via rejection sampling.
///
///
/// # Example
///
/// ```
/// use rand_distr::{UnitDisc, Distribution};
///
/// let v: [f64; 2] = UnitDisc.sample(&mut rand::thread_rng());
/// println!("{:?} is from the unit Disc.", v)
/// ```
#[derive(Clone, Copy, Debug)]
#[cfg_attr(feature = "serde1", derive(serde::Serialize, serde::Deserialize))]
pub struct UnitDisc;
impl<F: Float + SampleUniform> Distribution<[F; 2]> for UnitDisc {
#[inline]
fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> [F; 2] {
let uniform = Uniform::new(F::from(-1.).unwrap(), F::from(1.).unwrap());
let mut x1;
let mut x2;
loop {
x1 = uniform.sample(rng);
x2 = uniform.sample(rng);
if x1 * x1 + x2 * x2 <= F::from(1.).unwrap() {
break;
}
}
[x1, x2]
}
}