Microsoft Small Basic

Program Listing: PXF746

List Program

using System;
using System.Collections.Generic;
using Microsoft.SmallBasic.Library;
using Microsoft.SmallBasic.Library.Internal;
using System.Reflection;

namespace Jibba
{
///

/// The XMath object provides extra mathematical tools
///

[SmallBasicType]
public static class XMath
{
private static SievePrimes SievePrimes = new SievePrimes();

///

/// Gets an ascending list of prime numbers for a given range
///

/// The integer to start from
/// The integer to finish at
/// The boolean value to return the number of primes listed and how long it took.
/// Can be "true", "false" or "". Default "" is false
///
/// A CSV string of all primes in the range.
/// Throws an exception if 'to < from' or 'to < 2'.
/// Will be slower for very large ranges.
///
/// XMath.PrimeNumbers(0, 20000, "true")
public static Primitive PrimeNumbers(Primitive from, Primitive to, Primitive showStatistics)
{
Primitive output = "";

try { output = SievePrimes.GetAll(from, to, showStatistics); }

catch
{
string NL = Environment.NewLine;
string j = "Exception has occurred with:" + NL;
j += MethodBase.GetCurrentMethod().DeclaringType.Name.ToString() + ".";
j += MethodBase.GetCurrentMethod().Name + "()" + NL;

GraphicsWindow.Hide();
System.Media.SystemSounds.Exclamation.Play();
GraphicsWindow.ShowMessage(j, "Exception");
Program.End();
}

return output;
}
}

class SievePrimes
{
public string GetAll(Primitive from, Primitive to, Primitive showStatistics)
{
//cast primitives to c# types
string _showStatistics = (string)showStatistics;
bool statisticsRequested = false;

if (_showStatistics.ToLower() == "true")
statisticsRequested = true;

int rangeLowest = (int)System.Math.Max(2, from); //updated every 5k
int rangeHighest = (int)to;

List integers = new List();

//declare and init local var's
DateTime begin = DateTime.Now;
int count = 0, range = 5000; //range hangs at 100k use 5k
string k = "";
bool finished = false;

while (!finished) //The Sieve of Eratosthenes
{
if (rangeHighest - rangeLowest < range)
range = rangeHighest - rangeLowest;

integers.Capacity = range;

for (int i = rangeLowest; i <= rangeLowest + range; i++)
integers.Add(i);

for (int i = 2; i <= (rangeLowest + range) / 2; i++)
{
for (int j = 0; j < integers.Count; j++)
{
if (integers[j] % i == 0 && integers[j] > i) // % nearly 2x quicker than dbl Math.IEEERemainder
{
integers.Remove(integers[j]);
integers.Capacity--;
}
}
}

if (range < 5000 || range < 5000 && range < 1)
finished = true;

if (integers.Count != 0)
rangeLowest = (int)integers[integers.Count - 1] + 1;

k += string.Join(",", integers) + ",";
count += integers.Count;
integers.Clear();
}

TimeSpan elapsed = DateTime.Now - begin;

if (statisticsRequested)
{
k += Environment.NewLine;
k += String.Format("count: {0} | elapsed: {1}", count.ToString(), elapsed.ToString());
}

return k;
}
}
}