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if - You Are Special

Yesterday I told you that if is a function.

I lied.

In reality, if is a "special form".

I'll explain special forms in a minute, but let's just say that they're "special"!

Functions calls evaluate their arguments

Consider this code:

$ ys -e '
x =:
  DBG:
    add:
      sqr(4):DBG
      sqr(5):DBG
say: x
'
>>>16<<<
>>>25<<<
>>>41<<<
41

DBG is a function that prints its arguments and then returns the value of the last one.

We can see clearly that sqr(4) and sqr(5) are evaluated first, and then add is called with the results.

Let's try the same thing with if:

$ ys -e '
x =:
  DBG:
    if (rand(2):DBG > 1):DBG:
      sqr(4):DBG
      sqr(5):DBG
say: x
'
>>>1.288428806185308<<<
>>>true<<<
>>>16<<<
>>>16<<<
16

It looks like sqr(5) was never evaluated.

That's exactly how you want an if expression to work.

An if expression is a function that takes three arguments:

  • A "condition clause"
  • A "then clause"
  • An "else clause"

Based on the truthiness of the condition clause, only one of the other two clauses is evaluated.

This is true in practically any programming language.

About Special Forms

Most Lisp languages have special forms.

Special forms "look" like functions in that they use parentheses containing the form name and any arguments. But they are built into the language to behave differently.

YS has about a dozen special forms, and we've already been using them in this series. For example x =: y compiles into a Lisp def or let form (depending on the context) which are both special forms.

Fuggedaboudif!

Now that you know about special forms, you can forget about them.

In YS, everything's a function. A few of them are special. They all try to do the right thing.

Enjoy the rest of your weekend!

if - You Have to Ask!

Today we're going to look at the if command.

In a functional language, if statements are a bit different.

They'll, well, um... Functions.

So what's the big deal?

Functions have their own scope

So if if is a function then you can't use it to set state outside of its scope. Let me show you what I mean.

Consider this normal Python code:

$ python -c '
x = 500
if x > 100:
  size = "big"
else:
  size = "small"
print(size)
'
big

This will set size to "big" and then print it.

Let's try the same thing in YS:

$ ys -e '
x =: 500
if x > 100:
  size =: "big"
  size =: "small"
say: size
'
Error: Could not resolve symbol: size

Since if is a function, size is a local variable inside it's scope.

Well that's a bummer.

How are we supposed to get simple stuff done with YS?

It's simple once you've seen it:

$ ys -e '
x =: 500
size =:
  if x > 100:
    then: "big"
    else: "small"
say: size
'
big

We just need to make if return what we want and then assign it to a variable in the scope that we want it in.

But why then and else?

We didn't have them in the first example. Why did we need them in the second example?

Well actually we didn't need them.

But if I'm honest, right now I'm out in the woods (with wifi!) with friends who would rather have me hanging out doing Summer stuff than telling you about YS.

So we'll save that for later...

Maybe tomorrow!

YS Multi Functions

Many languages let you define functions with multiple signatures.

That is, you can have multiple functions with the same name but different arguments.

YS supports multi-arity functions. It dispatches on the number of arguments.

Let's see how it works.

Where the Funcs Have No Name

Any self-respecting functional language has a way to create anonymous functions.

In YS there are more than one!

Today we'll talk about nameless functions, why they are useful, and how to create and call them.

Functionally Speaking

YS is a functional programming language.

Therefore we should be able to write functions in YS.

This week I want to do a mini-series of blog posts about using and writing functions in YS.

Let's get started!

In The Beginning

How did YAML get started in the first place?

Today's Sunday post is about YAML, not YS.

But since YS is YAML, I think that's OK.

This is the story of how the YAML data language got its start as far back as 1999.

React and Comment here please!!!

I'm not sure how many people are reading this series, but I'm enjoying writing it. It's nice to know that I'm not alone on this Summer journey.

I recently added Reactions and Comments support to these blog posts. Scroll down to the bottom of each post to see them.

If you are enjoying the Summer of YS series, please don't forget to react (and comment if you want to) to let me know!

TMTOWTDI for YS Expressions

Like I said before, in YS, There's More Than One Way To Do It.

This is especially true for YS expressions.

Later on you'll learn that YS is a Lisp in disguise. In Lisp, an expression is a list consisting of a function and its arguments inside a set of parentheses.

Consider this Python code:

name = "World"
print("Hello, " + name + "!")

In a Lisp, this would be written as:

(def name "World")
(println (str "Hello, " name "!"))

In YS, this could be written as:

name =: 'World'
say: str('Hello, ' name '!')

I say could because... TMTOWTDI!

Today I'm going to show you many of the ways to DO IT in YS.

Loops and Strings

Yesterday I left you with a program that really needed to "YS up"!

$ ys -e '
url =:
  "https://github.com/dominictarr/random-name/raw/master/first-names.json"

people =: url.curl().json/load().shuffle().take(3)
shoes =: read("shoes.yaml").yaml/load()

say: str(people.0, " wears size ", shoes.0.size, " ", join([shoes.0.name, "s"]))
say: str(people.1, " wears size ", shoes.1.size, " ", join([shoes.1.name, "s"]))
say: str(people.2, " wears size ", shoes.2.size, " ", join([shoes.2.name, "s"]))
'

Let's make this awesome!

YS Curling (up North)

Ever been to Manitoba? I went there once when my flight from Seattle to Toronto diverted to Winnipeg because the plane's toilets stopped working! That's when I learned about the World's Largest Curling Rock.

Toronto DevOps Meetup

Speaking of Toronto, I'll be giving a talk called "The YS way to YAML" at the Toronto DevOps Meetup on June 12th. That's one week from today!

If you're in town I hope to see you there!

Today we'll be doing a little curling with YS.

Load and Compose your YAML Files

Probably the biggest problem people have with YAML is that everything has to be in one file. Things start off nice and clean, but as requirements grow, so do your files!

What if you could compose your YAML documents like you compose your code? Lots of small, single-purpose, possibly reusable files that you can load and compose together into the thing you need?

That's what YS is all about. As you know, YS is a functional language, and it has quite a few ways to load data (and code too, since Code is Data™!) from external sources.

Today we'll be looking at how to load things from disk files, including:

  • Other YS files
  • YAML files (YAML is YS)
  • JSON files (JSON is YAML)

You can also load things from CSV/TSV files, shell commands, databases, APIs, environment variables, and the web, but those are topics for another day.

YS YAML Documents

YAML files (aka YAML streams) can contain multiple "documents".

A YAML document is a top level mapping or sequence "node". Most YAML files contain a single document, but YAML files can contain multiple (or zero!) documents. New documents are started with a line of three dashes: ---.

YS can put these documents to all kinds of good use.

When you "load" a YAML file with YS, the result is the evaluation of the final document (by default). But since YS is functional, it can access any of the other documents.

Let's continue with yesterday's shoes example.

YAML Variables

YAML itself isn't a functional programming language, but advanced users are probably aware of YAML's anchors, aliases and the merge key.

The merge key is YAML's one functional thing, and it's actually not even part of the YAML 1.2 spec. However, people find it useful and many YAML implementations (including YS) support it.

The merge key (<<) is a special key that allows you to merge the contents of one mapping into another.

Today we'll explore the merge key a bit and show how variables can make it nicer to use.

The Summer of YS

Today starts a 3 month long, daily summertime journey into the intricacies of YAML and the wisdom of YS! Put on your favorite pair of coding sunglasses, grab a refreshing config drink, and let's get started!

Back in March I promised to start writing more often about all the ways that YS can help you out day-to-day with your YAML interactions. When I last posted here it was barely Spring and now Spring is turning into Summer.

Seasonal turning points be damned, I think of Summer as June, July, and August. In other words...

It's Summer dammit!

Let's declare this Summer, The Summer of YS!

  • in General
  • 2 min read

YAMLScript is YS!

Greetings! And welcome back to YAMLScript in 2025!

Or as we now say, YS in '25!.

It's been a minute since our last update, but we've been working super hard to make YS the best it can be.

Oh… What's "YS", you say?

Well, don't say "Y-S"…

Say "Wise"!

  • in General
  • 9 min read

The Kubernetes Effect

In my many years of creating Open Source software and talking about it at conferences, some of the most productive development times are often those leading up to the presentation.

In the last post, I mentioned that I was going to present a 90 minute YS tutorial at KubeCon (November 15th in Salt Lake City).

The conference was amazing and the YS tutorial was a huge success. I came away with the feeling that YAML and YS had found their community. KubeCon felt like YAMLCon!

  • in General
  • 6 min read

The Fall of YAMLScript!

(or Exciting YS News for Fall 2024!)

Greetings!

It's been over 3 months since the last blog post here.

Just to be clear, the YS/YAMLScript project is alive and fantastic!

We've just been busy as hell on 2 very big things: Exercism and KubeCon.

To be successful in both of these endeavors, YS needed to be amazing both as a programming language (Exercism) and as a data language (KubeCon).

There's so much new stuff to talk about, and I promise to write about all of it after things get back to a normal pace.

Today let's talk about Exercism, KubeCon and the positive impacts they've had on YS.

  • in General
  • 6 min read

Dr. StrangeYAML or How I Learned to Stop Worrying and Love the LLM

Well now, what happened is, uh, one of our data scientists, uh, well, he went a little funny in the head. You know. Just a little funny. And uh, he went and did a silly thing.

Well, I'll tell you what he did. He started chatting with computers... in YAML.

Well, let me finish, Elon.

Let me finish, Elon.

Well, listen, how do you think I feel about it?

  • in General
  • 8 min read

YS Spring Update

It's been a while since I let you know what's been happening with YS. I've been busy working on it every day this year and I have a lot to tell you about!

YS Activity in 2024

Let me start by telling you about some of the events that have happened in the YS world recently.

  • Seajure Talk - I gave a talk at the Seajure (Seattle Clojure) Meetup in March.
  • YS Article - The New Stack published an article about YS in March
  • YS Podcast - I was interviewed on the "The REPL" by Daniel Compton in April.

Finally I'm presenting a talk about YS at the Open Source Summit North America this Thursday, April 18th. Super excited about that!

  • in General
  • 4 min read

YS Firsts

Remember Your First Time?

Do you remember the first time you wrote a program in a new language? For YS, mine was yesterday!

This is my first post of 2024. I've been working on YS non-stop since the last YS Advent 2023 post. Too busy to write a blog post, I guess.

Yesterday something awesome happened.

Putting out a YS release is a complicated process. It takes me about an hour to do it. Of course I plan to automate it fully but I just haven't had the tuits.

For the last several releases, I've had a text file that listed all the steps so that I wouldn't forget anything. Yesterday I automated that list...

...you guessed it...

...in YS!