viete_pi_hex.rs

viete_pi_hex.rs

use std::f64::consts::PI;

/// Calculates an approximation of Pi using Viète's formula.
///
/// The formula is based on an infinite product of terms involving nested square roots.
/// This function approximates the product up to a given number of iterations.
///
/// # Arguments
///
/// * `iterations` - The number of terms to include in the product. More iterations
///                  lead to a more precise approximation.
///
/// # Returns
///
/// The calculated approximation of Pi as a `f64`.
fn viete_pi_approximation(iterations: u32) -> f64 {
    let mut product = 1.0;
    let mut current_sqrt_term = 0.0;

    for _ in 0..iterations {
        // Recursively calculate the next nested square root term.
        // For the first iteration, this is sqrt(2 + 0) = sqrt(2).
        // For subsequent iterations, it's sqrt(2 + previous_term).
        current_sqrt_term = (2.0f64 + current_sqrt_term).sqrt();

        // Multiply the next factor into the running product.
        // The factor is 2 divided by the current nested square root term.
        product *= 2.0 / current_sqrt_term;
    }

    // According to the formula, Pi is 2 times the infinite product.
    2.0 * product
}

fn main() {
    let iterations = u32::MAX / (u32::MAX / 999999999u32);
    let pi_approx = viete_pi_approximation(iterations);

    println!("Calculating Pi with Viète's formula:");
    println!("Number of iterations: {}", iterations);
    println!("Approximation of Pi: {}", pi_approx);
    println!("Actual Pi (from `std::f64::consts::PI`): {}", PI);
    println!("Difference: {}", (PI - pi_approx).abs());

    {
        let iterations = u32::MAX / (u32::MAX / 999999999u32);
        let pi_approx = viete_pi_approximation(iterations);

        println!("Calculating Pi with Viète's formula:");
        println!("Number of iterations: {}", iterations);
        println!("Approximation of Pi: {}", pi_approx);
        println!("Actual Pi (from `std::f64::consts::PI`): {}", PI);
        println!("Difference: {}\n", (PI - pi_approx).abs());

        // --- Requested Hex and Binary Output ---

        // Get the raw 64-bit unsigned integer representation of PI
        let pi_bits = PI.to_bits();

        println!("--- IEEE 754 Double-Precision (f64) Representation of PI ---");
        // :X prints the number in uppercase hexadecimal format
        println!("PI in Hexadecimal: {:X}", pi_bits);

        // :064b prints the number in binary, padded with leading zeros to 64 bits
        println!("PI in Binary (IEEE 754): {:064b}", pi_bits);
        // 0 [Sign] 10000000001 [Exponent] 0010010001000011111101101010100010001000010110100011000 [Fraction]
    }
}

https://play.rust-lang.org/?version=stable&mode=debug&edition=2024&gist=5764098aa008fc8c9808ed4d3ba857b0