Jonathan Starr's Blog

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Friday, January 25, 2008

improve my => 'code'

I just started playing around with LINQ seriously, and I really love some of the features incorporated, like the Enumerable.Range() function and how it can be used for integer programming.

Here's a simple function for generating lognormal distributions (could be useful for financial engineering).

Hope you're enjoying the samples,

Jonathan Starr

public List<double> GenerateLogNormalDistribution(int numberOfTimes, double mean, double standardDeviation)

{

Random randomGenerator = new Random();

var randomNumbers = from theNumbers in Enumerable.Range(1,

numberOfTimes).Select(x => randomGenerator.Next(1,

1000)/1000.0)

select theNumbers;

List<double> results = new List<double>();

randomNumbers.ToList().ForEach

(x => results.Add(mean + (standardDeviation * (Math.Sqrt(-2 * Math.Log(x)) * Math.Cos(6.28 * x)))));

return results;

}

posted @ Friday, January 25, 2008 8:00 PM | Feedback (3)

Surprising CLR Behavior

improve my => 'code'

The following code (surprise, surprise) compiles. But it does not work as intended (you won't be able to "doSomethingElse()!

Can any of you figure out why? (I have my suspicions.)

Jonathan Starr

using System;

namespace test

{

internal class BaseTest

{

private int _prop1;

public virtual int prop1

{

get { return _prop1; }

set { _prop1 = value; }

}

internal class DerivedTest : BaseTest

{

public override int prop1

{

set { base.prop1 = value; doSomethingElse(); }

}

posted @ Friday, January 25, 2008 4:45 PM | Feedback (0)

Response to Brainteaser #11?: I have been pretty excited about LINQ, because it seems to do all of the optimization for me for free (kinda like T-SQL).

Yow Han-Lee asks in his blog, Brainteaser #11, Given any two large List, what is the quickest way to find the mutual intersection of the two? Now take into consideration memory constraints?

Well, the answer that only takes a minute or two for me is the following...

Comments welcome!

Jonathan Starr

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace orderlisttest
{

    internal class Number
    {
        private int _Num1;
        public int Num1
        {
            get { return _Num1; }
            set { _Num1 = value; }
        }

        public Number(int theNumber)
        {
            this._Num1 = theNumber;
        }

    }
    public class start
    {

        public static void Main(string[] args)
        {
            var bigList1 = new List<Number>();
            var bigList2 = new List<Number>();

            for (int counter = 0; counter < 100000; counter++)
            {
                Random randomGenerator = new Random();
                int number = randomGenerator.Next(10000000);
                bigList1.Add(new Number(number));

                int number2 = randomGenerator.Next(10000000);
                bigList2.Add(new Number(number2));
            }

            var Found = from o1 in bigList1
                        join o2 in bigList2 on o1.Num1 equals o2.Num1
                        select new { o1.Num1 };

            Console.WriteLine(Found.Count().ToString() + " items were found in common.");
        }

     }

}; posted @ Friday, January 25, 2008 3:23 PM | Feedback (0)

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News: Jonathan Starr is a developer in Saint Louis, MO. He holds an MBA in Finance from Columbia Business School and earned his MCSD from Microsoft.

All statements in this blog are personal opinions and do not reflect the opinions of his employer.

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