From fd091b04316db9dc5fafadbd6bdbe60b127408a9 Mon Sep 17 00:00:00 2001
From: Daniel Mueller <deso@posteo.net>
Date: Thu, 2 Jan 2020 08:32:06 -0800
Subject: Update nitrokey crate to 0.4.0

This change finally updates the version of the nitrokey crate that we
consume to 0.4.0. Along with that we update rand_core, one of its
dependencies, to 0.5.1. Further more we add cfg-if in version 0.1.10 and
getrandom in version 0.1.13, both of which are now new (non-development)
dependencies.

Import subrepo nitrokey/:nitrokey at e81057037e9b4f370b64c0a030a725bc6bdfb870
Import subrepo cfg-if/:cfg-if at 4484a6faf816ff8058088ad857b0c6bb2f4b02b2
Import subrepo getrandom/:getrandom at d661aa7e1b8cc80b47dabe3d2135b3b47d2858af
Import subrepo rand/:rand at d877ed528248b52d947e0484364a4e1ae59ca502
---
 rand/rand_distr/src/unit_circle.rs | 99 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 99 insertions(+)
 create mode 100644 rand/rand_distr/src/unit_circle.rs

(limited to 'rand/rand_distr/src/unit_circle.rs')

diff --git a/rand/rand_distr/src/unit_circle.rs b/rand/rand_distr/src/unit_circle.rs
new file mode 100644
index 0000000..5863a1a
--- /dev/null
+++ b/rand/rand_distr/src/unit_circle.rs
@@ -0,0 +1,99 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use rand::Rng;
+use crate::{Distribution, Uniform, uniform::SampleUniform};
+use crate::utils::Float;
+
+/// Samples uniformly from the edge of the unit circle in two dimensions.
+///
+/// Implemented via a method by von Neumann[^1].
+///
+///
+/// # Example
+///
+/// ```
+/// use rand_distr::{UnitCircle, Distribution};
+///
+/// let v: [f64; 2] = UnitCircle.sample(&mut rand::thread_rng());
+/// println!("{:?} is from the unit circle.", v)
+/// ```
+///
+/// [^1]: von Neumann, J. (1951) [*Various Techniques Used in Connection with
+///       Random Digits.*](https://mcnp.lanl.gov/pdf_files/nbs_vonneumann.pdf)
+///       NBS Appl. Math. Ser., No. 12. Washington, DC: U.S. Government Printing
+///       Office, pp. 36-38.
+#[derive(Clone, Copy, Debug)]
+pub struct UnitCircle;
+
+impl<N: Float + SampleUniform> Distribution<[N; 2]> for UnitCircle {
+    #[inline]
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> [N; 2] {
+        let uniform = Uniform::new(N::from(-1.), N::from(1.));
+        let mut x1;
+        let mut x2;
+        let mut sum;
+        loop {
+            x1 = uniform.sample(rng);
+            x2 = uniform.sample(rng);
+            sum = x1*x1 + x2*x2;
+            if sum < N::from(1.) {
+                break;
+            }
+        }
+        let diff = x1*x1 - x2*x2;
+        [diff / sum, N::from(2.)*x1*x2 / sum]
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::Distribution;
+    use super::UnitCircle;
+
+    /// Assert that two numbers are almost equal to each other.
+    ///
+    /// On panic, this macro will print the values of the expressions with their
+    /// debug representations.
+    macro_rules! assert_almost_eq {
+        ($a:expr, $b:expr, $prec:expr) => (
+            let diff = ($a - $b).abs();
+            if diff > $prec {
+                panic!(format!(
+                    "assertion failed: `abs(left - right) = {:.1e} < {:e}`, \
+                     (left: `{}`, right: `{}`)",
+                    diff, $prec, $a, $b));
+            }
+        );
+    }
+
+    #[test]
+    fn norm() {
+        let mut rng = crate::test::rng(1);
+        for _ in 0..1000 {
+            let x: [f64; 2] = UnitCircle.sample(&mut rng);
+            assert_almost_eq!(x[0]*x[0] + x[1]*x[1], 1., 1e-15);
+        }
+    }
+
+    #[test]
+    fn value_stability() {
+        let mut rng = crate::test::rng(2);
+        let expected = [
+                [-0.9965658683520504, -0.08280380447614634],
+                [-0.9790853270389644, -0.20345004884984505],
+                [-0.8449189758898707, 0.5348943112253227],
+            ];
+        let samples: [[f64; 2]; 3] = [
+                UnitCircle.sample(&mut rng),
+                UnitCircle.sample(&mut rng),
+                UnitCircle.sample(&mut rng),
+            ];
+        assert_eq!(samples, expected);
+    }
+}
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