In the last episode we built a “Hello, World” application using gi-gtk-declarative. It’s now time to convert it into a to-do list application, in the style of TodoMVC. To convert the “Hello, World!” application to a to-do list application, we begin by adjusting our data types. The Todo data type represents a single item, with a Text field for …
In the last episode we explored gi-gtk, a package providing Haskell bindings to the GTK+ library, and noted in the end that the programming style was imperative and object-oriented. In this episode, we’ll program in a more functional style using gi-gtk-declarative. Our goal goal is to build a to-do list application, in the style of TodoMVC, using …
As described on its webpage, GTK+, or the GIMP Toolkit, is a multi-platform toolkit for creating user interfaces. In this video we will use the haskell-gi suite of packages to build a simple GTK+ application with Haskell. Show Notes We begin with an empty Cabal project called gtk-intro. To write our GTK+ application, we’re going to …
As described at the Cabal homepage, Cabal is a system for building and packaging Haskell libraries and programs. It defines a common interface for package authors and distributors to easily build their applications in a portable way. Cabal is part of a larger infrastructure for distributing, organizing, and cataloging Haskell libraries and programs.” In this video …
The Spock web framework for Haskell gives you a light but complete foundation to build web servers on, be it for traditional server-side rendered applications, or APIs for single-page applications. Compared to the Scotty framework, Spock is slightly richer in its feature set, and is more opinionated regarding the application architecture. In this episode we …
Testing the failure cases of code is often as important as testing the successful paths. The Pandoc filter we worked on in the previous episode returns its result, and throws exceptions with formatted strings, in the IO type. This makes testing the failure cases much harder. In this episode we will introduce a function exposing …
Testing Failure with Either Instead of Exception Read More »
Recently, before implementing a new feature in pandoc-include-code, a Pandoc filter I have written, I needed to make some changes to the code. The program allowed what should’ve been considered conflicting modes of operation. In this episode I’ll perform the same modification, to show you how the right data structure can guide and improve your …
Refactoring and Finding the Right Data Structure Read More »
Some viewers have asked me about validation in Haskell. There are multiple kinds of validation; checking that values have a certain structure, which is deterministic, and things like querying a database to see if a user name is already taken, which is effectful and indeterministic. Today, I’ll focus on simple deterministic validation using smart constructors. …
In the final part of the “Domain Modelling with Haskell” series we factor out recursion from the Project data type, and use Fixplate to traverse the tree and accumulate reports. Although a highly flexible and powerful technique, it should not be employed prematurely due to its more advanced nature. Show Notes Welcome to Haskell at …
Domain Modelling with Haskell: Factoring Out Recursion Read More »
This is the third episode in the short series on Domain Modelling with Haskell. Now our hypothetical customer requires reporting not only at the level of individual projects, but also on the project group level. Our previous solution using Traversable and Foldable won’t help us much, so we use explicit recursion and the WriterT monad …
Domain Modelling with Haskell: Accumulating with WriterT Read More »
