Utilities for prime numbers

With this module you can proof, if an integer is a prime. Or you can generate a seq[int] with all primes below an integer. The proof happens on the fly, or can be precomputed (sieve of Eratosthenes) when many calls are expected.

Installation

    nimble install primes

Sample usage

    echo isPrime(97)      # returns: true
    echo below(100).len() # returns: 25

Further examples can be found in the tests directory

API Documentation

• compute proof on the fly

    func isPrime*(n: int, primes: BitArray): bool =
  

• return a seq[int] with all primes below n

    func below*(n: int): seq[int] =
  

• generate a packed seq[bool] for all numbers < n

    func sieve*(n: int): BitArray =
  

• use precomputed sieve (if possible)

    func isPrime*(n: int, primes: BitArray): bool =
  

• return a seq[int] witth all primes below n with help of sieve

    proc below*(primes: BitArray, n: int): seq[int] =
  

• save the seq[bool] to a file

    proc saveSieve*(primes: BitArray, fileName: string) =
  

• load the seq[bool] from a previous created file

      proc loadSieve*(fileName: string): BitArray =
  

• load sieve if exits, or precompute sieve and save it

      proc sieve*(n: int, fileName: string): BitArray =