rand_simple/distributions/
bernoulli.rs

1use crate::create_state;
2use crate::standard_distributions::xorshift160_0_to_1;
3
4/// Bernoulli Distribution
5///
6/// # Example Usage
7/// ```
8/// let mut bernoulli = rand_simple::Bernoulli::new(1192u32);
9///
10/// // Default parameters
11/// assert_eq!(format!("{bernoulli}"), "Bernoulli(Probability) = Bernoulli(0.5)");
12/// println!("Does the event occur (1) or not (0) with a probability θ = 0.5? -> {}", bernoulli.sample());
13///
14/// // Updating the probability parameter
15/// let probability: f64 = 0.8f64;
16/// let result: Result<f64, &str> = bernoulli.try_set_params(probability);
17/// assert_eq!(format!("{bernoulli}"), "Bernoulli(Probability) = Bernoulli(0.8)");
18/// println!("Does the event occur (1) or not (0) with a probability θ = {}? -> {}", probability, bernoulli.sample());
19/// ```
20pub struct Bernoulli {
21    xyzuv: [u32; 5],  // 状態変数
22    probability: f64, // 発生確率
23}
24
25impl Bernoulli {
26    /// コンストラクタ
27    /// * `_seed` - 乱数の種
28    pub fn new(_seed: u32) -> Self {
29        let xyzuv: [u32; 5] = create_state(_seed);
30        Self {
31            xyzuv,
32            probability: 0.5_f64,
33        }
34    }
35
36    /// ある確率の事象が生じたか(1u64)、否か(0u64)を返す
37    pub fn sample(&mut self) -> u64 {
38        if xorshift160_0_to_1(&mut self.xyzuv) <= self.probability {
39            1_u64
40        } else {
41            0_u64
42        }
43    }
44
45    /// 確率変数のパラメータを変更する
46    /// * `probability` - 尺度母数
47    pub fn try_set_params(&mut self, probability: f64) -> Result<f64, &str> {
48        if !(0_f64..=1_f64).contains(&probability) {
49            Err("発生確率が0より小さいか、1よりも大きいです。確率変数のパラメータは前回の設定を維持します。")
50        } else {
51            self.probability = probability;
52            Ok(probability)
53        }
54    }
55}
56
57impl core::fmt::Display for Bernoulli {
58    /// Formatter for displaying in functions like println! macro
59    fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
60        write!(
61            f,
62            "Bernoulli(Probability) = Bernoulli({})",
63            self.probability
64        )?;
65        Ok(())
66    }
67}
rand_simple/distributions/bernoulli.rs

rand_simple/distributions/
bernoulli.rs
