# Crate bit_array [−] [src]

Collections implemented with bit arrays.

# Examples

This is a simple example of the Sieve of Eratosthenes which calculates prime numbers up to a given limit.

```extern crate typenum;
use bit_array::BitArray;
use typenum::{Unsigned, U10000};

// Store the primes as a BitArray
let primes = {
// Assume all numbers are prime to begin, and then we
// cross off non-primes progressively
let mut bv = BitArray::<u32, U10000>::from_elem(true);

// Neither 0 nor 1 are prime
bv.set(0, false);
bv.set(1, false);

for i in 2.. 1 + (U10000::to_usize() 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 >= U10000::to_usize() {
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, U10000::to_usize());
assert_eq!(num_primes, 1_229);```

## Structs

 BitArray The bitarray type. Blocks An iterator over the blocks of a `BitArray`. IntoIter Iter An iterator for `BitArray`.

## Traits

 BitsIn Traits for determing how many bits a primitive contains