Tomas Petricek

Searching for new ways of thinking in programming & working with data

I believe that the most interesting work is not the one solving hard problems, but the one changing how we think about the world. I follow this belief in my work on data science tools, functional programming and F# teaching, in my programming languages research and I try to understand it through philosophy of science.

The Gamma

I'm working on making data-driven storytelling easier, more open and reproducible at the Alan Turing Institute.

Consulting

I'm author of definitive F# books and open-source libraries. I offer my F# training and consulting services as part of fsharpWorks.

Academic

I published papers about theory of context-aware programming languages, type providers, but also philosophy of science.

Tomas Petricek
  • Tomas Petricek
  • Home
  • F# Trainings
  • Talks and books
  • The Gamma
  • Academic

Calculating with infinite sequences on MSDN

About a year ago, I wrote an article about using lazy computations in C# 3.0. It was published by the C# Community PM Charlie Calvert at the C# Developer Center. The article was a first of two articles where I wanted to demonstrate that C# 3.0 can be used for implementing useful constructs known from functional languages. I realized that I never posted the link to the second article to my blog, so you can find the annotation and link below.

However, I remembered about these two articles because I was just working on chapters 11 and 12 of the Real-world Functional Programming in .NET book that I’m writing. Lazy values, which were the topic of my first article, are discussed in the second part of chapter 11 and IEnumerable and F# sequences are the topic for the first part of chapter 12. Because I already wrote two articles on this topic, I had to think really hard to find better (and still simple enough) examples where these concepts are useful in practice. I also finally have enough space to show how these two concepts relate and talk about some interesting background – for example in Haskell, lazy sequences are in fact just ordinary lists that are lazy thanks to the Haskell nature.

A year ago, I definitely wouldn’t believe that today, I’ll be writing about the same topics, but this time as part of a book that has partly the same goal as these two articles – to show that functional programming ideas are really useful in the real-world and can enrich your programming toolbox (no matter whether you’re using C# or F# language). Anyway, here is the link to the second article – as usual when I look at something that I worked on a long time ago, I think I should rewrite it to make it better :-), but it still gives you an idea what is the book that I’m working on about:

My previous article explored lazy evaluation and looked at how it can be simulated in C#. We implemented a class Lazy<T>, which represents a value that can be evaluated on demand—this means that the class "knows" how to calculate the result, but doesn't actually calculate it until it is really needed in the program. One very interesting data structure known from functional programming that can be implemented using this lazy cell is a lazy list. Each element in a lazy list stores the value associated with the element (for example a number) and knows how to calculate the next element in the list, but it is lazy meaning that the next element is not calculated until its value is accessed by the program. The most interesting aspect of lazy lists is that they can be used for representing infinite sequences—this is possible because the elements are calculated only when needed and so the list will always store only a finite number of elements, but it will still be able to calculate the next element if it is needed.

In this article I will show that lazy lists can be implemented using the IEnumerable<T> type and I will also demonstrate how LINQ query operators can be used to manipulate infinite lists. Finally, we will look at an implementation of the Mandelbrot set program (you can see it on the screenshot) using the techniques described in this article.

You can read the complete article here: Calculating with Infinite Sequences in C# - C# Developer Center

By the way, I apologize for writing about the book all the time :-), but I hope you can understand that! I just "redirected" all my writing activities to the book, so the blog has been a little bit quiet and when I find the time to write something, it is usually inspired by working on the book, so I have to reference it… But I promise that the next couple of articles will be technical and I believe quite interesting!

Published: Thursday, 13 November 2008, 2:36 AM
Author: Tomas Petricek
Typos: Send me pull request!
Tags: c#, functional, universe, writing, links

Contact & about

This site is hosted on GitHub and is generated using F# Formatting and DotLiquid. For more info, see the website source on GitHub.

Please submit issues & corrections on GitHub. Use pull requests for minor corrections only.

  • Twitter: @tomaspetricek
  • GitHub: @tpetricek
  • Email me: tomas@tomasp.net

Blog archives

February 2019 (1),  November 2018 (1),  October 2018 (1),  May 2018 (1),  September 2017 (1),  June 2017 (1),  April 2017 (1),  March 2017 (2),  January 2017 (1),  October 2016 (1),  September 2016 (2),  August 2016 (1),  July 2016 (1),  May 2016 (2),  April 2016 (1),  December 2015 (2),  November 2015 (1),  September 2015 (3),  July 2015 (1),  June 2015 (1),  May 2015 (2),  April 2015 (3),  March 2015 (2),  February 2015 (1),  January 2015 (2),  December 2014 (1),  May 2014 (3),  April 2014 (2),  March 2014 (1),  January 2014 (2),  December 2013 (1),  November 2013 (1),  October 2013 (1),  September 2013 (1),  August 2013 (2),  May 2013 (1),  April 2013 (1),  March 2013 (1),  February 2013 (1),  January 2013 (1),  December 2012 (2),  October 2012 (1),  August 2012 (3),  June 2012 (2),  April 2012 (1),  March 2012 (4),  February 2012 (5),  January 2012 (2),  November 2011 (5),  August 2011 (3),  July 2011 (2),  June 2011 (2),  May 2011 (2),  March 2011 (4),  December 2010 (1),  November 2010 (6),  October 2010 (6),  September 2010 (4),  July 2010 (3),  June 2010 (2),  May 2010 (1),  February 2010 (2),  January 2010 (3),  December 2009 (3),  July 2009 (1),  June 2009 (3),  May 2009 (2),  April 2009 (1),  March 2009 (2),  February 2009 (1),  December 2008 (1),  November 2008 (5),  October 2008 (1),  September 2008 (1),  June 2008 (1),  March 2008 (3),  February 2008 (1),  December 2007 (2),  November 2007 (6),  October 2007 (1),  September 2007 (1),  August 2007 (1),  July 2007 (2),  April 2007 (2),  March 2007 (2),  February 2007 (3),  January 2007 (2),  November 2006 (1),  October 2006 (3),  August 2006 (2),  July 2006 (1),  June 2006 (3),  May 2006 (2),  April 2006 (2),  December 2005 (1),  July 2005 (4),  June 2005 (5),  May 2005 (1),  April 2005 (3),  March 2005 (3),  January 2005 (1),  December 2004 (3),  November 2004 (2), 

License

Unless explicitly mentioned, all articles on this site are licensed under Creative Commons Attribution Share Alike. All source code samples are licensed under the MIT License.

CC License logo