Your First Dewy Program

Create a directory for the program:

mkdir -p ~/code/greetings
cd ~/code/greetings

Create greetings.dewy with this source:

let greet = (name:string):>void =>
    printl"Hello, {name}!"

let names = ["Ada" "Grace" "Linus"]

loop name in names
    greet(name)

Run it:

dewy greetings.dewy

The output is:

Hello, Ada!
Hello, Grace!
Hello, Linus!

This small program already shows several recurring parts of Dewy:

• let introduces a binding;
• (name:string):>void => ... defines a function with one string parameter;
• whitespace separates array elements, so commas are unnecessary;
• loop name in names consumes the array from left to right;
• {name} interpolates a value into a string;
• printl prints text followed by a newline.

The one-line traditional greeting is valid too:

printl'Hello, World!'

Juxtaposing a callable with its argument can express a call, so this is equivalent to printl('Hello, World!').

Top-Level Code and main

Dewy executes top-level code in source order. A small program therefore needs no special entry wrapper.

When a module declares main, its top level still initializes first and Dewy calls main afterward:

const application_name = "notes"

let main = ():>int64 => {
    printl"starting {application_name}"
    return 0
}

An explicit top-level main() is an ordinary call; it does not replace automatic entry invocation.

For ordinary use, dewy compiles and runs the program in one command. The hosted compiler lowers Dewy to µDewy, after which the selected µDewy backend produces the executable form.