Code shared from the Rust Playground

playground.rs

struct Probability {
    value: f64,
}

impl Probability {
    fn new(p: f64) -> Self {
        assert!(
            (0.0..=1.0).contains(&p),
            "Probability must be between 0 and 1"
        );
        Self { value: p }
    }
}

/// Calculates P(A|B) using Bayes' Theorem: P(A|B) = (P(B|A) * P(A)) / P(B)
fn bayes_theorem(p_b_given_a: f64, p_a: f64, p_b: f64) -> f64 {
    (p_b_given_a * p_a) / p_b
}

fn main() {
    let p_a = 0.10; // Prior: Probability of having a rare disease
    let p_b_given_a = 0.99; // Likelihood: Test is 99% accurate for positive cases
    let p_b = 0.05; // Evidence: Total probability of testing positive

    let result = bayes_theorem(p_b_given_a, p_a, p_b);
    println!("The probability of A given B is: {:.2}%", result * 100.0);
}