| lib.rs |
# Description
Dynamic collections implemented with compact bit vectors.
# Examples
This is a simple example of the [Sieve of Eratosthenes][sieve]
which calculates prime numbers up to a given limit.
[sieve]: http://en.wikipedia.org/wiki/Sieve_of_Eratosthenes
```
use bit_vec::BitVec;
let max_prime = 10000;
// Store the primes as a BitVec
let primes = {
// Assume all numbers are prime to begin, and then we
// cross off non-primes progressively
let mut bv = BitVec::from_elem(max_prime, true);
// Neither 0 nor 1 are prime
bv.set(0, false);
bv.set(1, false);
for i in 2.. 1 + (max_prime as f64).sqrt() as usize {
// if i is a prime
if bv[i] {
// Mark all multiples of i as non-prime (any multiples below i * i
// will have been marked as non-prime previously)
for j in i.. {
if i * j >= max_prime {
break;
}
bv.set(i * j, false)
}
}
}
bv
};
// Simple primality tests below our max bound
let print_primes = 20;
print!("The primes below {} are: ", print_primes);
for x in 0..print_primes {
if primes.get(x).unwrap_or(false) {
print!("{} ", x);
}
}
println!();
let num_primes = primes.iter().filter(|x| *x).count();
println!("There are {} primes below {}", num_primes, max_prime);
assert_eq!(num_primes, 1_229);
``` |
95458 |