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Welcome to FP Haskell Center

Welcome to FP Haskell Center
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Haskell web programming update: updated for Yesod 1.2 tl;dr: A simple Yesod tutorial. Yesod is a Haskell web framework. You shouldn’t need to know Haskell. Why Haskell? Its efficiency (see Snap Benchmark & Warp Benchmark). Haskell is a high level language that makes it harder to shoot yourself in the foot than C, C++ or Java, for example. “If your program compiles it will be very close to what the programmer intended”. Haskell web frameworks handle parallel tasks perfectly—even better than node.js, for example. From a purely technical point of view, Haskell seems to be the perfect web development tool. Hard to grasp HaskellHard to find a Haskell programmerThe Haskell community is smaller than the community for /. I won’t say these are not important drawbacks. Actually there are three main Haskell web frameworks: I don’t think there is a real winner between these three framework. Why did I write this article? During this tutorial you’ll install, initialize, and configure your first Yesod project. Install Initialize

lisperati There's other tutorials out there, but you'll like this one the best for sure: You can just cut and paste the code from this tutorial bit by bit, and in the process, your new program will create magically create more and more cool graphics along the way... The final program will have less than 100 lines of Haskell[1] and will organize a mass picnic in an arbitrarily-shaped public park map and will print pretty pictures showing where everyone should sit! (Here's what the final product will look like, if you're curious...) The code in this tutorial is a simplified version of the code I'm using to organize flash mob picnics for my art project, picnicmob... [1] - Lines of active code only, not counting optional function signatures.

Yesod Web Framework for Haskell Haskell comme un vrai! tlpl: Un tutoriel très court mais très dense pour apprendre Haskell. Merci à Oleg Taykalo vous pouvez trouver une traduction Russe ici: Partie 1 & Partie 2 ; Table of Content Je pense vraiment que tous les développeurs devraient apprendre Haskell. La plupart des langages partagent les mêmes fondamentaux : les variablesles bouclesles pointeursles structures de données, les objets et les classes Haskell est très différent. Plier son esprit à Haskell peut être difficile. Cet article sera certainement difficile à suivre. La manière conventionnelle d’apprendre Haskell est de lire deux livres. Cet article fait un résumé très dense et rapide des aspect majeurs d’Haskell. Pour les francophones ; je suis désolé. Cet article contient cinq parties : Note: Chaque fois que vous voyez un séparateur avec un nom de fichier se terminant par lhs, vous pouvez cliquer sur le nom de fichier et télécharger le fichier. 01_basic/10_Introduction/00_hello_world.lhs Introduction Install Tools: Don’t be afraid Functional

Lenses In Pictures - You should know what a functor is before reading this post. Read this to learn about functors. Suppose you want to make a game: Ok, now how would you move this player? moveX (Mario (Point xpos ypos)) val = Mario (Point (xpos + val) ypos) Instead, lenses allow you to write something like this: location.x `over` (+10) $ player1 Or this is the same thing: over (location . x) (+10) player1 Lenses allow you to selectively modify just a part of your data: Much clearer! location is a lens. Fmap You probably know how fmap works, Doctor Watson (read this if you don’t): Well old chap, what if you have nested functors instead? You need to use two fmaps! Now, you probably know how function composition works: What about function composition composition? “If you want to do function composition where a function has two arguments”, says Sherlock, “you need (.).(.)!” “That looks like a startled owl”, exclaims Watson. “Indeed. The type signature for function composition is: (.) :: (b -> c) -> (a -> b) -> (a -> c) Setters

Wadler: Monads Philip Wadler The arrow calculus Sam Lindley, Philip Wadler, and Jeremy Yalloop, Journal of Functional Programming 20(1):51&em;69, 2010. We introduce the arrow calculus, a metalanguage for manipulating Hughes’s arrows with close relations both to Moggi’s metalanguage for monads and to Paterson’s arrow notation. Arrows are classically defined by extending lambda calculus with three constructs satisfying nine (somewhat idiosyncratic) laws; in contrast, the arrow calculus adds four constructs satisfying five laws (which fit two well-known patterns). The five laws were previously known to be sound; we show that they are also complete, and hence that the five laws may replace the nine. Available in: pdf, doi. Monadic constraint programming Tom Schrijvers, Peter Stuckey, and Philip Wadler Journal of Functional Programming 19(6):663&em;697, 2009. A constraint programming system combines two essential components: a constraint solver and a search engine. Available in: pdf, doi. Available in: pdf.

HaskellWiki The Scala Programming Language Everything Your Professor Failed to Tell You About Functional Programming I've been trying to learn Haskell lately, and the hardest thing seems to be learning about monads. "Monads in Ruby" and "Monads for Functional Programming" helped me finally to break the ice, but more importantly, they gave me a glimpse behind the veil. I finally began to understand something that is trivial to people such as Philip Wadler, but something that never had been explained to me so succinctly. Monads as a Design Pattern Somewhere, somebody is going to hate me for saying this, but if I were to try to explain monads to a Java programmer unfamiliar with functional programming, I would say: "Monad is a design pattern that is useful in purely functional languages such as Haskell. Philip Wadler says, "Monads provide a convenient framework for simulating effects found in other languages, such as global state, exception handling, output, or non-determinism." The Java programmer could argue fairly, "Hey, Java has all those things, and monads aren't even mentioned in Design Patterns. A Little Lens Starter Tutorial lens is a package which provides the type synonym Lens which is one of a few implementations of the concept of lenses, or functional references. lens also provides a number of generalizations of lenses including Prisms, Traversals, Isos, and Folds. Lenses and their cousins are a way of declaring how to focus deeply into a complex structure. They form a combinator library with sensible, general behavior for things like composition, failure, multiplicity, transformation, and representation. Lenses let you apply some of the power of libraries like hxt to all data types in all programs that you write. As this comparison suggests, the initial steps might be very complicated, but, unlike hxt, lenses are ubiquitous enough to make learning the complexity pay off over time. The end result is a way to efficiently construct and manipulate "methods of poking around inside things" as simple first-class values. A lens is a first-class reference to a subpart of some data type. Yep. Any more examples? ...