News
A monitoring server demonstrates using queues to communicate between threads, and using sockets to communicate between processes. This page in the Haskell Phrasebook covers a more complete and realistic program than the others we’ve written so far, and so it is a good bit longer than the rest.
Functortown continues its study of the notion of applicative functors as contexts for computation. Previously we talked about the Functor for the function type – or, more precisely, for (->) a, the partially applied function type. In this lesson we again discuss functions, this time looking at the Applicative instance often referred to as reader.
A lot of software has to deal with time in some form or another. Moments in time covers basic parsing and conversion operations for UTC times and Unix timestamps. Thanks to Taylor Fausak for submitting this example code during Hacktoberfest!
We’ve been giving a lot of thought lately to how to present some of the more exotic language extensions – like GADTs, type families, and rank-N types – and we’ve decided to start by focusing not on the individual extensions one at a time, but rather with the more broad aim of “getting a more sophisticated understanding of the type system.” We still plan to make a reference page for each extension, but the more important place to start if you’re entirely unfamiliar with these features will be the new atypical data constructors series. It begins with a lesson on type equality constraints, which will then lead naturally into understanding what GADTs are and what they’re useful for.
We’ve added two new lessons to the the Validation course, thus making all of the book’s content available to Type Classes members. One lesson is about using coerce safely and effectively for newtype-heavy code, while the other is an introduction to the lens library through the prisms in the validation package.
This week, we’ve added content to two of our courses, Functortown and Validation. The Functortown lesson is called Zippy applicatives and discusses the two list applicatives: the normal one, and ZipList. Second, as many of our subscribers are aware, we had turned the Validation course into a book, and we made that free to anyone who was subscribed to Type Classes at the time when we published the book. The book included two chapters that did not appear on the site, however. The first of those, now added to the course, is on Coercible. We expect to add the final chapter next week, so all that content will be available to all our subscribers. Enjoy!
Courses
Courses are series about a particular topic meant to be watched in order. Some are more theory-and-fundamentals oriented, while some focus on building a project. Each course has clearly identified prerequisites and goals, to help you choose which courses are right for you.
Text and ByteString types.Functor, Bifunctor, Applicative, Traversable, Monad, Contravariant, and Profunctor, with motivating examples and discussions of what each is good for, the laws governing each, and how to property test instances.fltkhs and Chris using gtk3. Each lesson explains aspects of the library, illuminates important Haskell concepts such as concurrency primitives and implicit parameters, and gives you some basis for comparing libraries for your own native GUI application projects.Maybe, Either, and Validation types brings, as well as using newtype to differentiate inputs. We also demonstrate the difference between Applicative and Monad.Reference
Each article explains a single, sometimes small, Haskell topic in detail. Some articles include video. Haskell reference pages supplement, but are independent of, the courses and projects. Haskellers of any level will find them useful as reference.
ReaderT from the transformers library and use it to illustrate type aliases, newtypes, and various approaches for typeclass deriving, using the GeneralizedNewtypeDeriving and DerivingVia GHC extensions.TypeApplications lets you visibly apply functions to type arguments. We demonstrate several common use cases.ScopedTypeVariables lets you extend the scope of a type variable over a whole function, including its subexpressions.Transitions
Switching to Haskell doesn’t mean you have to start over learning how to code. Our transitions content is geared toward explaining how concepts from other languages relate to Haskell, so you can advantage of what you already know as you get started in Haskell. We focus on Java, JavaScript, and Python.
Math.max() < Math.min() and what it has to do with monoids. This is a two-part article covering Haskell’s folds (compared to JavaScript reduce), monoids, and identity values.scotty, a Haskell web framework.Tooling
This section covers topics that aren’t about the Haskell language itself, but about software that helps you be more productive with it.
:type command and never be at a loss for knowledge of typesghcid