Sieve of Eratosthenes

sieveOfEratosthenes.rs

use std::io;
use std::num;

fn main () {
    // ... use stuff from num library
    let mut input    = String::new();
    let mut a: Vec<bool> = Vec::new();
    let mut n: i64       = 0;
    println!("Please enter a number");
    match io::stdin().read_line(&mut input) {
        Ok(t) => {
            input.pop();
            if t > 15 { return; }
            println!("{} is the input", input);
            n = input.parse::<i64>().unwrap();
        }
        Err(error) => println!("error: {}", error),
    }
    for number in 0..n {
        a.push(true);
    }
    println!("{:?}", a);
    println!("{} is n", n);
    let sqrt = (n as f64).sqrt() as i64 + 1;
    for i in 2..sqrt as i64 {
        if a[i] == true {
            let mut j = i*2;
            while j < n {
                a[j] = false;
                j += i;
            }
        }
    }
}



// Input: an integer n > 1.
//
// Let A be an array of Boolean values, indexed by integers 2 to n,
// initially all set to true.
//
// for i = 2, 3, 4, ..., not exceeding √n:
//   if A[i] is true:
//     for j = i2, i2+i, i2+2i, i2+3i, ..., not exceeding n:
//       A[j] := false.
//
// Output: all i such that A[i] is true.