Posts in the “scala” category

A few days ago I shared the source code for a simple Akka remote actor example. In that example I showed how to communicate between actors in two different JVMs using Scala and Akka. In that example I showed how to communicate between the two JVMs using String messages because I didn’t want to make the example any harder than necessary.

Today, I’m taking that example just one step further to show how to communicate between actors on different JVMs by using custom objects for your messages.

In the Scala Standard Library, a Future is a data structure used to retrieve the result of some concurrent operation. This result can be accessed synchronously (blocking) or asynchronously (non-blocking).

~ from the akka.io docs

(For more information, here’s my Scala Futures example.)

I woke up this morning (June 7, 2013) thinking it must be about 200 days to Christmas. Foregoing any simple ways to determine that, I decided it would be a good time to use the nscala-time library, a Scala wrapper around Joda Time.

Sticking with the time theme, I haven’t much free time today, so without further ado, here is some Scala code that determines the number of days between today and Christmas:

I get to have another operation (surgery) next week, but I still hope to have the next version of my book on Scala and functional programming available by the end of the month.

SBT 1.0.0 is now available. See this Lightbend page for more details.

I was doing a little Scala programming this morning, and because I hadn't written any code in a while, I managed to forget how isInstanceOf works with inheritance in Scala.

To refresh my memory, I wrote the following example code:

As a quick note, I was just looking into the state of Scala “lint” tools, and found ScalaStyle, WartRemover, and Scapegoat.

This 2014 underscore.io post states, “Those interested in FP purity in a Scala world, you’ll want WartRemover.” (Of course that recommendation may have changed by now.) The current ScalaStyle website states, “Scalastyle is used as part of the grading framework for the course Functional Programming Principles in Scala by Martin Odersky on Coursera.”

While reading the excellent Scala/FP book, Advanced Scala with Cats, I was just reminded that Scala’s Either class was redesigned in Scala 2.12. Prior to 2.12, Either was not biased, and didn’t implement map and flatMap methods. As the image from the book shows, Either is redesigned in 2.12 to include those methods, so it can now be used in Scala for-expressions as shown.

(I write about biasing in my book, Learning Functional Programming in Scala.)

I haven’t used Scala Native yet, but at v0.1 it looks very cool. The image is from scala-lang.org, you can read much more about it at scala-native.org, and follow the developers here on Twitter.

Today (June 30, 2017) is the last day to buy “Learning Functional Programming in Scala” for $10. The price goes up to $25 tonight, and $30 on August 1st.

Last call: My new book, Learning Functional Programming in Scala, goes up to $30 tonight (August 1, 2017).

A decent article: Ten things Idris improved over Haskell. I noticed that Martin Odersky tweeted this, and mentioned that Scala made the same improvements.

Scala 2.12.3 has been released, and compiler performance has improved significantly.

I’m not yet sure if I like the book Functional and Reactive Domain Modeling, but one thing is for sure: I couldn’t begin to understand it if I didn’t first do the research to write Learning Functional Programming in Scala. The author immediately jumps into monads as if they are commonly understood, and also designs his functions as “modules” in a very Haskell-ish way. I’m not saying the book is bad, just that it has a high barrier to entry.

The image is from an article titled, Why I don’t regret moving our Android app to Scala.

If you ever wanted to get access to global operating system keystrokes from a Java or Scala Swing application, you can do it with the jnativehook library. Here’s a short demo:

Here’s the full Scala source code for the demo. I put a few comments in the code to highlight the important areas:

In my new book on functional programming in Scala, I’m not a salesman trying to “sell” anyone on functional programming. I prefer to think of myself as a reporter who reports what he has learned. I describe this as the reporter metaphor.

On Twitter this morning I saw this post by Pablo Fco. Pérez where he compared some Bash commands to Scala. In particular he noted that this awk command:

awk '{print $1}'

is equivalent to:

map(_.split(" ").head)

The next release of my book on Scala and functional programming will include at least two lessons on ScalaCheck.

The sbt-errors-summary plugin looks cool. Here’s a summary from its author:

“A simple plugin that makes the error reporter a bit more concise. I find it useful when doing refactoring: I get a lot of compilation errors, and I waste a lot of time switching between files and looking for line numbers in the error message, when I can immediately see what's wrong when looking at the faulty line.”