A few decades before modern computers were invented, the mathematician Alonzo Church developed a language called the lambda calculus. He intended it as a tool for investigating the foundations of mathematics. The first person to realize the practical connection between programming and the lambda calculus was John McCarthy, who created Lisp in 1958. 6 comments

During the 1960s, computer scientists began to recognise and study the importance of the lambda calculus. Peter Landin and Christopher Strachey developed ideas about the foundations of programming languages: how to reason about what they do (operational semantics) and how to understand what they mean (denotational semantics). 1 comment

In the early 1970s, Robin Milner created a more rigorous functional programming language named ML. While ML was developed to help with automated proofs of mathematical theorems, it gained a following for more general computing tasks. 1 comment

The 1970s saw the emergence of lazy evaluation as a novel strategy. David Turner developed SASL and KRC, while Rod Burstall and John Darlington developed NPL and Hope. NPL, KRC and ML influenced the development of several more languages in the 1980s, including Lazy ML, Clean, and Miranda. 4 comments

By the late 1980s, the efforts of researchers working on lazy functional languages were scattered across more than a dozen languages. Concerned by this diffusion of effort, a number of researchers decided to form a committee to design a common language. After three years of work, the committee published the Haskell 1.0 specification in 1990. It named the language after Haskell Curry, an influential logician. 1 comment

Many people are rightfully suspicious of “design by committee”, but the work of the Haskell committee is a beautiful example of the best work a committee can do. They produced an elegant, considered language design, and succeeded in unifying the fractured efforts of their research community. Of the thicket of lazy functional languages that existed in 1990, only Haskell is still actively used. 11 comments

Since its publication in 1990, the Haskell language standard has seen five revisions, most recently in 1998. A number of Haskell implementations have been written, and several are still actively developed. 6 comments

During the 1990s, Haskell served two main purposes. On one side, it gave language researchers a stable language in which to experiment with making lazy functional programs run efficiently. Other researchers explored how to construct programs using lazy functional techniques. Still others used it as a teaching language. 4 comments

While these basic explorations of the 1990s proceeded, Haskell remained firmly an academic affair. The informal slogan of those inside the community was to “avoid success at all costs”. Few outsiders had heard of the language at all. Indeed, functional programming as a field was quite obscure. 3 comments

During this time, the mainstream programming world experimented with relatively small tweaks: from programming in C, to C++, to Java. Meanwhile, on the fringes, programmers were beginning to tinker with new, more dynamic languages. Guido van Rossum designed Python; Larry Wall created Perl; and Yukihiro Matsumoto developed Ruby. 10 comments

As these newer languages began to seep into wider use, they spread some crucial ideas. The first was that programmers are not merely capable of working in expressive languages; in fact, they flourish. The second was in part a byproduct of the rapid growth in raw computing power of that era: it's often smart to sacrifice some execution performance in exchange for a big increase in programmer productivity. Finally, several of these languages borrowed from functional programming. 4 comments

Over the past half a decade, Haskell has successfully escaped from academia, buoyed in part by the visibility of Python, Ruby, and even Javascript. The language now has a vibrant and fast-growing culture of open source and commercial users, and researchers continue to use it to push the boundaries of performance and expressiveness. 10 comments

If you're looking for a Haskell library to use for a particular task, or an application written in Haskell, check out the following resources. 1 comment

There are a number of ways you can get in touch with other Haskell programmers, to ask questions, learn what other people are talking about, and simply do some social networking with your peers. No comments

I had a great deal of fun working with John and Don. Their independence, good nature, and formidable talent made the writing process remarkably smooth. No comments

Simon Peyton Jones took a chance on a college student who emailed him out of the blue in early 1994. Interning for him over that summer remains a highlight of my professional life. With his generosity, boundless energy, and drive to collaborate, he inspires the whole Haskell community. No comments

My children, Cian and Ruairi, always stood ready to help me to unwind with wonderful, madcap little-boy games. No comments

Finally, of course, I owe a great debt to my wife, Shannon, for her love, wisdom, and support during the long gestation of this book. No comments

I am so glad to be able to work with Bryan and Don on this project. The depth of their Haskell knowledge and experience is amazing. I enjoyed finally being able to have the three of us sit down in the same room -- over a year after we started writing. No comments

My 2-year-old Jacob, who decided that it would be fun to use a keyboard too, and is always eager to have me take a break from the computer and help him make some fun typing noises on a 50-year-old Underwood typewriter. No comments

Most importantly, I wouldn't have ever been involved in this project without the love, support, and encouragement from my wife, Terah. No comments

Before all else, I'd like to thank my amazing co-conspirators, John and Bryan, for encouragment, advice and motivation. No comments

My colleagues at Galois, Inc., who daily wield Haskell in the real world, provided regular feedback and war stories, and helped ensured a steady supply of espresso. 1 comment

My PhD supervisor, Manuel Chakravarty, and the PLS research group, who provided encouragement, vision and energy, and showed me that a rigorous, foundational approach to programming can make the impossible happen. No comments

And, finally, thanks to Suzie, for her insight, patience and love. No comments

We developed this book in the open, posting drafts of chapters to our web site as we completed them. Readers then submitted feedback using a web application that we developed. By the time we finished writing the book, about 800 people had submitted over 7,500 comments, an astounding figure. 1 comment

We deeply appreciate the time that so many people volunteered to help us to improve our book. Their encouragement and enthusiasm over the 15 months we spent writing made the process a pleasure. No comments

The breadth and depth of the comments we received have profoundly improved the quality of this book. Nevertheless, all errors and omissions are, of course, ours. 1 comment

The following people each contributed over 1% of the total number of review comments that we received. We would like to thank them for their care in providing us with so much detailed feedback. No comments

Alex Stangl, Andrew Bromage, Brent Yorgey, Bruce Turner, Calvin Smith, David Teller, Henry Lenzi, Jay Scott, John Dorsey, Justin Dressel, Lauri Pesonen, Lennart Augustsson, Luc Duponcheel, Matt Hellige, Michael T. Richter, Peter McLain, Rob deFriesse, RГјdiger Hanke, Tim Chevalier, Tim Stewart, William N. Halchin. No comments

We are also grateful to the people below, each of whom contributed at least 0.2% of all comments. No comments

Achim Schneider, Adam Jones, Alexander Semenov, Andrew Wagner, Arnar Birgisson, Arthur van Leeuwen, Bartek Ćwikłowski, Bas Kok, Ben Franksen, Björn Buckwalter, Brian Brunswick, Bryn Keller, Chris Holliday, Chris Smith, Dan Scott, Dan Weston, Daniel Larsson, Davide Marchignoli, Derek Elkins, Dirk Ullrich, Doug Kirk, Douglas Silas, Emmanuel Delaborde, Eric Lavigne, Erik Haugen, Erik Jones, Fred Ross, Geoff King, George Moschovitis, Hans van Thiel, Ionuț Arțăriși, Isaac Dupree, Isaac Freeman, Jared Updike, Joe Thornber, Joeri van Eekelen, Joey Hess, Johan Tibell, John Lenz, Josef Svenningsson, Joseph Garvin, Josh Szepietowski, Justin Bailey, Kai Gellien, Kevin Watters, Konrad Hinsen, Lally Singh, Lee Duhem, Luke Palmer, Magnus Therning, Marc DeRosa, Marcus Eskilsson, Mark Lee Smith, Matthew Danish, Matthew Manela, Michael Vanier, Mike Brauwerman, Neil Mitchell, Nick Seow, Pat Rondon, Raynor Vliegendhart, Richard Smith, Runar Bjarnason, Ryan W. Porter, Salvatore Insalaco, Sean Brewer, Sebastian Sylvan, Sebastien Bocq, Sengan Baring-Gould, Serge Le Huitouze, Shahbaz Chaudhary, Shawn M Moore, Tom Tschetter, Valery V. Vorotyntsev, Will Newton, Wolfgang Meyer, Wouter Swierstra. 1 comment

We would like to acknowledge the following people, many of whom submitted a number of comments. 1 comment

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Overdiep, Brendan Macmillan, Brett Morgan, Brian Bloniarz, Brian Lewis, Brian Palmer, Brice Lin, C Russell, Cale Gibbard, Carlos Aya, Chad Scherrer, Chaddaï Fouché, Chance Coble, Charles Krohn, Charlie Paucard, Chen Yufei, Cheng Wei, Chip Grandits, Chris Ball, Chris Brew, Chris Czub, Chris Gallagher, Chris Jenkins, Chris Kuklewicz, Chris Wright, Christian Lasarczyk, Christian Vest Hansen, Christophe Poucet, Chung-chieh Shan, Conal Elliott, Conor McBride, Conrad Parker, Cosmo Kastemaa, Creighton Hogg, Crutcher Dunnavant, Curtis Warren, D Hardman, Dafydd Harries, Dale Jordan, Dan Doel, Dan Dyer, Dan Grover, Dan Orias, Dan Schmidt, Dan Zwell, Daniel Chicayban Bastos, Daniel Karch, Daniel Lyons, Daniel Patterson, Daniel Wagner, Daniil Elovkov, Danny Yoo, Darren Mutz, Darrin Thompson, Dave Bayer, Dave Hinton, Dave Leimbach, Dave Peterson, Dave Ward, David Altenburg, David B. Wildgoose, David Carter, David Einstein, David Ellis, David Fox, David Frey, David Goodlad, David Mathers, David McBride, David Sabel, Dean Pucsek, Denis Bueno, Denis Volk, Devin Mullins, Diego Moya, Dino Morelli, Dirk Markert, Dmitry Astapov, Dougal Stanton, Dr Bean, Drew Smathers, Duane Johnson, Durward McDonell, E. Jones, Edwin DeNicholas, Emre Sevinc, Eric Aguiar, Eric Frey, Eric Kidd, Eric Kow, Eric Schwartz, Erik Hesselink, Erling Alf, Eruc Frey, Eugene Grigoriev, Eugene Kirpichov, Evan Farrer, Evan Klitzke, Evan Martin, Fawzi Mohamed, Filippo Tampieri, Florent Becker, Frank Berthold, Fred Rotbart, Frederick Ross, Friedrich Dominicus, Gal Amram, Ganesh Sittampalam, Gen Zhang, Geoffrey King, George Bunyan, George Rogers, German Vidal, Gilson Silveira, Gleb Alexeyev, Glenn Ehrlich, Graham Fawcett, Graham Lowe, Greg Bacon, Greg Chrystall, Greg Steuck, Grzegorz Chrupała, Guillaume Marceau, Haggai Eran, Harald Armin Massa, Henning Hasemann, Henry Laxen, Hitesh Jasani, Howard B. Golden, Ilmari Vacklin, Imam Tashdid ul Alam, Ivan Lazar Miljenovic, Ivan Miljenovic, J. Pablo Fernández, J.A. Zaratiegui, Jaap Weel, Jacques Richer, Jake McArthur, Jake Poznanski, Jakub Kotowski, Jakub Labath, James Cunningham, James Smith, Jamie Brandon, Jan Sabbe, Jared Roberts, Jason Dusek, Jason F, Jason Kikel, Jason Mobarak, Jason Morton, Jason Rogers, Jeff Balogh, Jeff Caldwell, Jeff Petkau, Jeffrey Bolden, Jeremy Crosbie, Jeremy Fitzhardinge, Jeremy O'Donoghue, Jeroen Pulles, Jim Apple, Jim Crayne, Jim Snow, Joan Jiménez, Joe Fredette, Joe Healy, Joel Lathrop, Joeri Samson, Johannes Laire, John Cowan, John Doe, John Hamilton, John Hornbeck, John Lien, John Stracke, Jonathan Guitton, Joseph Bruce, Joseph H. 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Mulligan, S Pai, Sam Lee, Sandy Nicholson, Scott Brickner, Scott Rankin, Scott Ribe, Sean Cross, Sean Leather, Sergei Trofimovich, Sergio Urinovsky, Seth Gordon, Seth Tisue, Shawn Boyette, Simon Brenner, Simon Farnsworth, Simon Marlow, Simon Meier, Simon Morgan, Sriram Srinivasan, Sriram Srinivasan, Stefan Aeschbacher, Stefan Muenzel, Stephan Friedrichs, Stephan Nies, Stephan-A. Posselt, Stephyn Butcher, Steven Ashley, Stuart Dootson, Terry Michaels, Thomas Cellerier, Thomas Fuhrmann, Thomas Hunger, Thomas M. DuBuisson, Thomas Moertel, Thomas Schilling, Thorsten Seitz, Tibor Simic, Tilo Wiklund, Tim Clark, Tim Eves, Tim Massingham, Tim Rakowski, Tim Wiess, Timo B. Hübel, Timothy Fitz, Tom Moertel, Tomáš Janoušek, Tony Colston, Travis B. Hartwell, Tristan Allwood, Tristan Seligmann, Tristram Brelstaff, Vesa Kaihlavirta, Victor Nazarov, Ville Aine, Vincent Foley, Vipul Ved Prakash, Vlad Skvortsov, Vojtěch Fried, Wei Cheng, Wei Hu, Will Barrett, Will Farr, Will Leinweber, Will Robertson, Will Thompson, Wirt Wolff, Wolfgang Jeltsch, Yuval Kogman, Zach Kozatek, Zachary Smestad, Zohar Kelrich. 3 comments

Finally, we wish to thank those readers who submitted over 800 comments anonymously. 4 comments