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Event sourcing + free monads = free sourcing?

I recently wrote about Event Sourcing and Free Monads. The natural next step is combining the two! How would a free monad adjusted for event sourcing look like? Please bear in mind that the below is just really a draft, not a complete solution. Hence any suggestions for improvements are very welcome! But, let’s review the basic assumptions. Our application ...

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Ceylon: Why you might want to choose Ceylon

In a couple of days Ceylon 1.2 will be released, after a year of development. That’s exciting for us, but we think it would be interesting to summarize our thoughts about why you should be excited about Ceylon, and why you might consider it over other programming languages designed to run on the Java and JavaScript virtual machines. Ceylon is ...

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Scala extractors infix sample with Rational numbers

I keep coming back to the awesome introductory material on Scala put together by Daniel Westheide. One of the examples that he provides for extractors using an infix operation pattern is the Streams API – val xs = 58 #:: 43 #:: 93 #:: Stream.empty xs match {   case first #:: second #:: _ => first - second   ...

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Clojure web development – state of the art – part 2

This is part 2 of my “Clojure web development” series. You can discuss first part on this reddit thread. After reading the comments I must explain two assumptions I had writing this series: Keep things easy to understand for people from outside Clojure land, especially Java devs. That’s why I use REST/JSON in favor of transit and component as a ...

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Akka Typed: First steps with typed actors in Scala

With the [release of Akka 2.4.0| http://akka.io/news/] a couple of weeks ago the experimental Akka Typed module was added. With Akka Typed it is possible to create and interact with Actors in a type safe manner. So instead of just sending messages to an untyped Actor, with Akka Typed we can add compile time type checking to our Actor interactions. ...

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Testing Asynchronous Code

Asynchronous code is hard. Everyone knows that. Writing asynchronous tests is even harder. Recently I fixed a flaky test and I want to share some thoughts about writing asynchronous tests. In this post we explore a common problem with asynchronous tests—how to force a test to take a specific ordering between threads, and forcing some operations by some threads to ...

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Integration testing with Gradle

Unit testing works automatically using Gradle, but if you would like to have a separate set of integration tests you need to do a small exercise. Actually they don’t have to be integration tests at all. This guide shows you how to configure Gradle to use any kind of tests and run them independently from others. I will use Scala ...

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Listen to notifications from Postgresql with Scala

In the past I’ve written a couple of articles (Building a REST service in Scala with Akka HTTP, Akka Streams and reactive mongo and ReactiveMongo with Akka, Scala and websockets) which used MongoDB to push updates directly from the database to a Scala application. This is a very nice feature if you just want to subscribe your application to a ...

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