Files
adler32
aho_corasick
alga
approx
ascii
atty
backtrace
backtrace_sys
base64
bitflags
blas_src
block_buffer
block_padding
brotli2
brotli_sys
buf_redux
byte_tools
byteorder
cauchy
cblas_sys
cfg_if
chrono
chunked_transfer
colored
crc32fast
crossbeam
crossbeam_channel
crossbeam_deque
crossbeam_epoch
crossbeam_queue
crossbeam_utils
ctrlc
deflate
digest
dirs
error_chain
filetime
futures
generic_array
getrandom
gzip_header
hex
httparse
hyper
idna
itoa
language_tags
lapack_src
lapacke
lapacke_sys
lazy_static
libc
libm
linked_hash_map
log
matches
matrixmultiply
maybe_uninit
md5
memchr
memoffset
mime
mime_guess
multipart
nalgebra
base
geometry
linalg
ndarray
ndarray_linalg
net2
netlib_src
nix
num_complex
num_cpus
num_integer
num_rational
num_traits
opaque_debug
percent_encoding
phf
phf_shared
ppv_lite86
proc_macro2
quick_error
quote
rand
rand_chacha
rand_core
rand_distr
rawpointer
regex
regex_syntax
remove_dir_all
rosrust
rosrust_codegen
rosrust_msg
rouille
rustc_demangle
rustros_tf
ryu
safemem
scopeguard
serde
serde_bytes
serde_derive
serde_json
serde_xml_rs
sha1
siphasher
smallvec
syn
tempdir
term
thread_local
threadpool
time
tiny_http
traitobject
twoway
typeable
typenum
ucd_util
unicase
unicode_bidi
unicode_normalization
unicode_xid
url
utf8_ranges
void
xml
xml_rpc
yaml_rust
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
// Copyright 2019 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 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)]
pub struct UnitDisc;

impl<N: Float + SampleUniform> Distribution<[N; 2]> for UnitDisc {
    #[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;
        loop {
            x1 = uniform.sample(rng);
            x2 = uniform.sample(rng);
            if x1*x1 + x2*x2 <= N::from(1.) {
                break;
            }
        }
        [x1, x2]
    }
}

#[cfg(test)]
mod tests {
    use crate::Distribution;
    use super::UnitDisc;

    #[test]
    fn value_stability() {
        let mut rng = crate::test::rng(2);
        let expected = [
                [0.018035709265959987, -0.4348771383120438],
                [-0.07982762085055706, 0.7765329819820659],
                [0.21450745997299503, 0.7398636984333291]
            ];
        let samples: [[f64; 2]; 3] = [
                UnitDisc.sample(&mut rng),
                UnitDisc.sample(&mut rng),
                UnitDisc.sample(&mut rng),
            ];
        assert_eq!(samples, expected);
    }
}