CFLib.org – Common Function Library Project

Description:
Each call to the function returned from createPrimeNumberSequence() returns the next prime number.

Return Values:
Returns a function which when called returns the next prime number

Example:

component extends="testbox.system.BaseSpec" {

    function beforeAll(){
        include "udfs/createPrimeNumberSequence.cfm";
    }

    function run(){
        describe("Tests for createPrimeNumberSequence()", function(){
            it("returns primes", function(){
                var primeSequence = createPrimeNumberSequence();
                var primes = [];
                for (var i=1; i++ <= 10;){
                    primes.append(primeSequence());
                }
                expect(
                    primes
                ).toBe([2,3,5,7,11,13,17,19,23,29]);
            });
        });
    }

}

Parameters:

No arguments.

Full UDF Source:

/**
 * Creates a "generator" for returning prime numbers, in sequence
 * 
 * @return Returns a function which when called returns the next prime number 
 * @author Adam Cameron (dac.cfml@gmail.com) 
 * @version 1.1, October 17, 2014 
 */
function createPrimeNumberSequence(){
    var primes = [2]
    var potential = 1

    return function(){
        while (true) {
            potential += 2
            var upperThresholdToCheck = sqr(potential)
            var potentialIsPrime = true
            for (var prime in primes){
                request.called++
                if (potential mod prime == 0) {
                    potentialIsPrime = false
                    break;
                }
                if (prime > upperThresholdToCheck) break;
            }
            if (potentialIsPrime) {
                primes.append(potential)
                return primes[primes.len()-1]
            }
        }
    }
}