Julia functions for computing prime numbers.

At the moment, this repository just contains the following functions which have been duplicated from Base Julia:

factor(n) -> Dict

Compute the prime factorization of an integer n. Returns a dictionary. The keys of the dictionary correspond to the factors, and hence are of the same type as n. The value associated with each key indicates the number of times the factor appears in the factorization.

julia> factor(100) # == 225*5 Dict{Int64,Int64} with 2 entries: 2 => 2 5 => 2

isprime(x::Integer) -> Bool

Returns true if x is prime, and false otherwise.

julia> isprime(3) true

isprime(x::BigInt, [reps = 25]) -> Bool

Probabilistic primality test. Returns true if x is prime with high probability (pseudoprime); and false if x is composite (not prime). The false positive rate is about 0.25^reps. reps = 25 is considered safe for cryptographic applications (Knuth, Seminumerical Algorithms).

julia> isprime(big(3)) true

primes([lo,] hi)

Returns a collection of the prime numbers (from lo, if specified) up to hi.

primesmask([lo,] hi)

Returns a prime sieve, as a BitArray, of the positive integers (from lo, if specified) up to hi. Useful when working with either primes or composite numbers.

To avoid naming conflicts with Base, these are not exported for Julia version 0.4. In this case you will need to explicitly import the symbols:

using Primes
import Primes: isprime, primes, primesmask, factor