jkg_prime.cpp

#include <iostream>
#include <math.h>
#include <vector>

bool is_prime(int n){
	if(n<2) return false;
	if(n==2) return true;
	if (!(n & 1)) return false;

	int stop_n = floor(sqrt(n));
	for(int i=3;i < stop_n;i+=2){
		if(n%i==0) return false;
	}
	return true;
}

//this implemention found here: http://www.geeksforgeeks.org/sieve-of-eratosthenes/
void markMultiples(int * arr,int a,int n){
	int i=2,num;
	while ((num = i*a)<=n)
	{
		arr[num-1]=1;
		i++;
	}
}

std::vector<int> sieve(int n){
	int *arr = new int[n];
	std::vector<int> solution;
	std::memset(arr,0,n*(sizeof(int)));
	for (int i=1;i<n;i++){
		if (arr[i]==0)
		{
			solution.push_back(i+1);
			markMultiples(arr,i+1,n);
		}
	}
	delete[] arr;
	return solution;

jkg_prime.h

bool is_prime(int n);
void markMultiples(int * arr,int a,int n);
std::vector<int> sieve(int n);

jkg_prime.i

%module jkg_prime
%{
	#include "jkg_prime.h"
%}

%include "jkg_prime.h"
%include "typemaps.i"
%include "std_vector.i"
%template(IntVector) std::vector<int>;

setup.py

from distutils.core import setup, Extension
import numpy
import os

os.environ['CC'] = 'g++';
setup(name='jkg_prime', version='1.0', ext_modules =[Extension('_jkg_prime',
 ['jkg_prime.cpp', 'jkg_prime.i'], swig_opts=['-c++'], include_dirs = [numpy.get_include(),'.'])])

test.py

import jkg_prime

print(list(jkg_prime.sieve(30)))
if jkg_prime.is_prime(29):
  print('yay')