Scala, Java, Unix, MacOS tutorials (page 11)

In a dream this morning
I’m pushing a little unpowered vacuum/sweeper
like you see them use at Denny’s
or maybe Cracker Barrel.

And then I look up
and see two young girls
and they’re singing a pretty song.

I ask what the song is
and they giggle a little,
and one asks the other
if they should tell me,
and she says yes.

So they tell me that there’s this
old abandoned house
and sometimes when they go by it
they see an old woman pushing
a sweeper like this.

Functional Programming FAQ: What are the benefits of an Effect System, like ZIO?

Answer

I’m currently planning a video on “The benefits of an Effect System in computer programming” on my free Scala and functional programming videos website, but in case I don’t get around to making that video, here are the slides I have put together.

Also, if you’d like to see a video that is somewhat similar, here’s my popular “What is ZIO 2?” video on YouTube.

Background

If you haven’t heard of Effects or an Effects System, I wrote about them a long time ago here. Also, in book, Effect-Oriented Programming, the authors describe them this way:

• Effects are the unpredictable parts of a system.
• Effect Systems partition the unpredictable parts, and manage them separately from the predictable ones.

I did a “gratitude” meditation exercise two nights ago, and it ended up going almost four hours. (Fortunately for me, at advanced levels you can trade some meditation time for sleep.)

The technique is to put your mind in the area of your heart and express things you’re thankful for, including this crazy body I have, all of you, and in the end, basically everything.

If it helps you can start by feeling love for one being — such as Zeus — and work out from there.

A soul that temporarily has a body

At some point it really hits you that I’m some soul that’s pushing this vehicle that was named “Alvin” around, and YOU are also some other individual soul. So when YOU don’t do what I want, that’s okay, because you’re another student here in Earth School. Basically, MY soul needs to give YOUR soul that freedom to work your stuff out.

I noticed that the ZIO 2 ZIO.fromOption method returns Option[Nothing] as its error type, so I asked my friend Claude about it, and got the following response, which I have cleaned up a little.

Scala FAQ: What is the Nothing type in Scala, and how do I use it?

Solution

In Scala, the Nothing type is called a bottom type, which means it is a sub-type of every other type in the Scala type system. It is also specifically a data type that has no instances.

In practical use, Nothing is used to indicate that a computation or function will never produce a result normally, either because it throws an exception, enters an infinite loop, or encounters some other abnormal termination.

Visually, this is what the Nothing type looks like in the Scala type hierarchy (image courtesy of this scala-lang.org page):

Scala: Common uses of Nothing

Some common use cases of Nothing in Scala include:

If you’ve ever seen the “Maine Cabin Masters” tv show, you may have seen the black flag that they fly on their cabins while they’re working on them. If you ever wondered about their black flag, here’s what I can tell you from this deleted scene video:

• In the video, which was posted on March 19, 2020, Ryan states that the flag is new.
• The flag signifies the Maine Cabin Masters “are here” and “we’re kicking butt on this project, and it’s going to be the best this camp will ever be.”
• It is the Maine Cabin Masters “skull and crossbones.”
• The image is a Chase Morrill design.

As I work more with ZIO 2, I also find myself thinking a lot about the ZIO 2 mental model, by which I partially mean “a way of thinking about your code” and also “ZIO 2 best practices.”

Here are my initial notes. Also, I hope that most of this code is mine, but several snippets are from other sources that I don’t remember, including the official ZIO 2 docs.

I know that I may never get to any “final” stages of enlightenment, but IMHO and as near as I can tell from my current meditation practice level, the last steps leading up to enlightenment/awakening/liberation are:

Scala 3 FAQ: What are opaque types in Scala?

Discussion

I previously wrote a little about Opaque Types in Scala 3, and today, as I’m working on a new video about opaque types, I thought I’d add some more information about them.

After my first-ever bought with diverticulitis, I wanted to make notes about what happened over the last five days.

Monday, April 7, 2015

On April 7, 2015, I woke up at 3:30am with pain and discomfort in my lower-left abdomen. I knew something was wrong, but I didn’t know what it was. It felt like a golf ball was lodged in there, and several hours later it was still there.