Alexandru Nedelcu - Blog

Defining an EffectRuntime that is used to build IO effects.

It’s me, facing a hard to solve problem.

Unlawful/independent version of cats.effect.Effect from Cats Effect v2.

For separating integration tests, from unit tests, in build.sbt: // sbt command-line shortcut addCommandAlias("ci-integration", "Integration/testOnly -- -n integrationTest") lazy val IntegrationTest = config("integration").extend(Test) //... lazy val ro…

Converts an Akka Streams Flow into an In => IO[Out] method, thus wrapping Flow into Cats-Effect’s IO. import akka.actor.ActorSystem import akka.stream.Materializer import akka.stream.scaladsl.Flow import cats.effect.{ ContextShift, IO, Resource } import c…

My son ❤️ Today it's my 38ᵗʰ birthday.

See: Securely Store Sensitive Data in RAM import cats.effect.{ Resource, Sync } import java.util.ConcurrentModificationException import java.util.concurrent.atomic.AtomicBoolean final case class PasswordValue(value: String) { override def toString = "P…

sealed abstract class KnownException(message: String, cause: Throwable) extends RuntimeException(message, cause) sealed abstract class InputException(message: String, cause: Throwable) extends KnownException(message, cause) object InputException {…

Remote debugging can be used to debug externally executed programs, useful to activate in sbt in order to keep using it while debugging with your favorite IDE.

Demonstrating Typescript’s untagged union types: type Left = { either: "left" value: L } type Right = { either: "right", value: R } type Either = Left | Right function left(value: L): Either { return { either: "left", value } } function right(va…

In the face of errors, we could interrupt what we are doing and log the incident for debugging purposes.

Cats-Effect’s Resource can’t be converted directly into a Reactive Streams Publisher.

// Demonstrating that directly executing runnables in your // ExecutionContext is a really bad idea def trigger(cycles: Int): Future[Int] = { implicit val directEC = new ExecutionContext { def execute(r: Runnable) = r.run() def reportF…

The best practices are those enforced by the build tools, as part of the build process.

This is a simple, but very effective implementation of a Semaphore, used for easily parallelizing work in JavaScript/TypeScript.

Video link (open on YouTube.com) I love writing.

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Article explains how to have fine grained control over replacements when using String.replaceAll or similar in Java or Scala.

type Callback = (a: A) => void; /** * Delays stuff for ensuring fairness. */ export function yieldRunLoop(): Promise { const fn: (cb: (() => void)) => void = typeof setImmediate !

Monix Task implementation for wrapping (suspending) blocking I/O such that it can be canceled. s Imported from gist.github.com.

When you use isInstanceOf[Class] checks, that’s an anti-pattern, as Scala has a much better way of discriminating between types.

The Bifunctor IO data type is a hot topic in the Scala community.

This article is about OOP hierarchies, in comparisson with type classes, using as example Scala’s standard collections, which are involved in a recent debate around their redesign. 1.

Minitest is my minimal testing library that I’ve been using for developing Monix.

Functional Programming (FP) is programming with functions.

Video link (open on YouTube.com) Presentation from Scala Days, held in Chicago and Copenhagen: Slides (PDF file) Video (YouTube) Video link (open on YouTube.com) Abstract Scala’s Future from the standard library is great, but sometimes we need more.

This piece of code will leak memory and eventually crash your Node.js process or browser: // Tested on Node.js 7.10, Firefox 57 and Chrome 61 // // Usage of `setImmediate` is to prove that we have // async boundaries, can be removed for browsers // not su…

Builds and deployments of new versions and snapshots is a pain.

My presentation from the Bucharest FP meetup.

Asynchrony is everywhere and it subsumes concurrency.

The venerable Iterator interface we all love and hate could use some improvements.

Given there’s a Scala collection redesign discussion going on, it’s a good time to talk about one of my personal pet peeves: the existence of Traversable in the standard library, along with its variants like TraversableLike and TraversableOnce.

I’m using NewsBlur.com for consuming RSS feeds.

The Monix Task was heavily inspired by scalaz.concurrent.Task and by scala.concurrent.Future.

Video link (open on YouTube.com) Video link (open on YouTube.com) Akka & Monix: Controlling Power Plants - my presentation from the Typelevel Summit, Oslo, 2016: Slides (PDF file) Video (YouTube) Also see: Monix Task, flatMap(Oslo), 2016 the Monix project…

Video link (open on YouTube.com) Video link (open on YouTube.com) Monix Task: Lazy, Async & Awesome - my presentation from flatMap(Oslo) 2016: Slides (PDF file) Video (YouTube) Also see: Akka & Monix, Typelevel Summit, Oslo, 2016 Monix project Abstract Sc…

I’m a man of strong opinions and I truly believe that when we are doing mocking, stubbing, dependency injection and integration testing, such practices represent clear signals for code smell, meaning code that sucks as a symptom of a bigger problem, one of

Back in June I attended Scala Days in Amsterdam and participated at a talk by Mathias Doenitz on The Reactive Streams Implementation Landscape.

This is a collection of best practices for Scala, something to get you started.

Getting started with a new programming language shouldn't be hard, however navigating the web for resources on getting started with Scala can be a doubting experience, as many such resources are either out of date, or wrong, or both.

The AtomicReference is like a container for a volatile reference.

Multithreading is a pain to deal with.

Client-side JavaScript development can be quite overwhelming, even for senior developers.

I’ve been following the excellent Coursera course on Functional Programming Principles in Scala led by Martin Odersky.

In machine learning a classifier is able to predict, given an input, a probability distribution over a set of categories.

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I had a very specific need for fetching the details for some apps in the Android marketplace, in an automated manner.