Hello, Dada!

Following on my Fun with Dada post, this post is going to start teaching Dada. I’m going to keep each post short – basically just what I can write while having my morning coffee.¹

You have the right to write code

Here is a very first Dada program

println("Hello, Dada!")

I think all of you will be able to guess what it does. Still, there is something worth noting even in this simple program:

“You have the right to write code. If you don’t write a main function explicitly, one will be provided for you.” Early on I made the change to let users omit the main function and I was surprised by what a difference it made in how light the language felt. Easy change, easy win.

Convenient is the default

Here is another Dada program

let name = "Dada"
println("Hello, {name}!")

Unsurprisingly, this program does the same thing as the last one.

“Convenient is the default.” Strings support interpolation (i.e., {name}) by default. In fact, that’s not all they support, you can also break them across lines very conveniently. This program does the same thing as the others we’ve seen:

let name = "Dada"
println("
    Hello, {name}!
")

When you have a " immediately followed by a newline, the leading and trailing newline are stripped, along with the “whitespace prefix” from the subsequent lines. Internal newlines are kept, so something like this:

let name = "Dada"
println("
    Hello, {name}!
    
    How are you doing?
")

would print

Hello, Dada!

How are you doing?

Just one familiar String

Of course you could also annotate the type of the name variable explicitly:

let name: String = "Dada"
println("Hello, {name}!")

You will find that it is String. This in and of itself is not notable, unless you are accustomed to Rust, where the type would be &'static str. This is of course a perennial stumbling block for new Rust users, but more than that, I find it to be a big annoyance – I hate that I have to write "Foo".to_string() or format!("Foo") everywhere that I mix constant strings with strings that are constructed.

Similar to most modern languages, strings in Dada are immutable. So you can create them and copy them around:

let name: String = "Dada"
let greeting: String = "Hello, {name}"
let name2: String = name

Next up: mutation, permissions

OK, we really just scratched the surface here! This is just the “friendly veneer” of Dada, which looks and feels like a million other languages. Next time I’ll start getting into the permission system and mutation, where things get a bit more interesting.