sum_phi.rs

sum_phi.rs

// A placeholder function for a_k.
// YOU WILL NEED TO REPLACE THIS WITH YOUR ACTUAL DEFINITION OF a_k.
fn get_a_k(_k: i32) -> f64 {
    // Example: For demonstration, let's just return 1.0 for all k.
    // In a real scenario, this could be:
    // - a value from a lookup table (e.g., if a_k is stored in a Vec)
    // - a result of a mathematical formula (e.g., k! or 1/k)
    // - a coefficient of a specific series (e.g., Fourier series, Taylor series)
    1.0
}

fn main() {
    // Define the value of phi.
    // We'll use the golden ratio as an example, but you can change it.
    let phi: f64 = 1.618033988749895; // Golden ratio approximation

    // Define the summation range.
    let k_start: i32 = -100;
    let k_end: i32 = 100;
    // Initialize the sum.
    let mut n: f64 = 0.0;

    // Perform the summation from k_start to k_end.
    for k in k_start..=k_end {
        let a_k = get_a_k(k);
        let phi_power_k = phi.powi(k); // Calculate phi^k

        n += a_k * phi_power_k;
    }

    // Print the result.
    println!("Summation range: k = {} to {}", k_start, k_end);
    println!("Value of phi: {}", phi);
    println!("Calculated n: {}", n);

    // --- Example demonstrating how get_a_k might be replaced ---
    // If a_k values were stored in a vector for a specific range:
    // let a_values_lookup: Vec<f64> = vec![
    //     /* a_k for k=-1000 */ 1.0,
    //     /* a_k for k=-999 */ 0.9,
    //     // ... hundreds of values ...
    //     /* a_k for k=0 */ 5.0,
    //     // ... hundreds of values ...
    //     /* a_k for k=1000 */ 0.1,
    // ];
    //
    // fn get_a_k_from_vec(k: i32, start_k_of_vec: i32, lookup_vec: &[f64]) -> f64 {
    //     let index = (k - start_k_of_vec) as usize;
    //     if index < lookup_vec.len() {
    //         lookup_vec[index]
    //     } else {
    //         // Handle out of bounds or default value
    //         0.0
    //     }
    // }
    //
    // // Then in main, you would call:
    // // let a_k = get_a_k_from_vec(k, k_start, &a_values_lookup);
}