The newer and much longer version of this article is now available: Monads explained in C# (again)

It looks like there is a mandatory post that every blogger who learns functional programming should write: what a Monad is. Monads have the reputation of being something very abstract and very confusing for every developer who is not a hipster Haskell programmer. They say that once you understand what a monad is, you loose the ability to explain it in simple language. Doug Crockford was the first one to lay this rule down, but it becomes kind of obvious once you read 3 or 5 explanations on the web. Here is my attempt, probably doomed to fail :)

My exploration of Actor model started with Akka.NET framework - a .NET port of JVM-based Akka. Actor programming model made a lot of sense to me, but once I started playing with it, some questions arose. Most of those questions were related to the following definition:

How many times did you write a SQL to save a row without knowing whether the same primary key already exists or not? You just get an object in your data access layer and you want to save all fields into the database.

Immutable data structures provide a lot of benefits to programmers, especially when representing domain value objects. Immutability is an essential part of functional programming paradigm. The concept is useful in object-oriented languages too, but you have to pay some price to get this advantage.

Dependency Inversion is one of the five principles of widely known and acknowledged S.O.L.I.D. design guidelines. This principle is very powerful and useful when applied consistently. But in my experience, it’s actually quite easy to misunderstand the idea, or at least to mentally simplify it to somewhat less profound technique of Dependency Injection.

This is the fifth part of Building a Poker Bot series where I describe my experience developing bot software to play in online poker rooms. I’m building the bot with .NET framework and F# language which makes the task relatively easy and very enjoyable. Here are the previous parts:

Aurelia is a modern and slick single-page application framework. “Single-page application” aspect means that it’s loaded into the browser once, and then the navigation happens on the client side and all the data are loaded from a REST API endpoint.

F# and Scala are quite similar languages from 10.000 feet view. Both are functional-first languages developed for the virtual machines where imperative languages dominate. C# for .NET and Java for JVM are still lingua franca, but alternatives are getting stronger.

Azure Application Insights is an analytics service to monitor live web applications, diagnose performance issues, and understand what users actually do with the app. Aurelia is a modern and slick single-page application framework. Unfortunately, there’s not much guidance on the web about how to use AppInsights and Aurelia together in a proper manner. The task gets even more challenging in case you are using TypeScript and want to stay in type-safe land. This post will set you up and running in no time.

Azure SQL Database is a managed cloud database-as-a-service. It provides application developers with SQL Server databases which are hosted in the cloud and fully managed by Microsoft.

Yesterday I’ve published a simple Leaflet plugin called leaflet-corridor. The plugin defines a new Leaflet primitive L.Corridor.

When initialized with an array of geo points and width, it renders a polyline with width fixed in meters, not in pixels. That means that line width changes whenever zoom level changes.

Event Sourcing is an approach, when an append-only store is used to record the full series of events that describe actions taken on a particular domain entity. This event store becomes the main source of truth to reconstruct the current state of the entity and its complete history.

The post was published for F# Advent Calendar 2016, thus the examples are themed around the Christmas gifts.

This article is my naive introduction to the data processing discipline called Stream Processing.