YS / YAMLScript

Add Logic to Your YAML Files

Synopsis

Load file.yaml with YS:

!YS-v0:

# Get data from external sources:
names-url =:
  'github:dominictarr/random-name/first-names.json'

name-list =: names-url:curl:json/load

# Data object with literal keys and generated values:
name:: name-list:shuffle:first
aka:: name-list:rand-nth
age:: &num 2 * 3 * 7
color:: &hue
  rand-nth: qw(red green blue yellow)
title:: "$(*num) shades of $(*hue)."

and get:

{
  "name": "Dolores",
  "aka": "Anita",
  "age": 42,
  "color": "green",
  "title": "42 shades of green."
}

Description

YS is a functional programming language with a clean YAML syntax.

YS can be used for enhancing ordinary YAML files with functional operations, such as:

• Import (parts of) other YAML files to any node
• String interpolation including function calls
• Data transforms including ones defined by you

This YS library should be a drop-in replacement for your current YAML loader!

Most existing YAML files are already valid YS files. This means that YS works as a normal YAML loader, but can also evaluate functional expressions if asked to.

Under the hood, YS code compiles to the Clojure programming language. This makes YS a complete functional programming language right out of the box.

Even though YS compiles to Clojure, and Clojure compiles to Java, there is no dependency on Java or the JVM. YS is compiled to a native shared library (libys.so) that can be used by any programming language that can load shared libraries.

To see the Clojure code that YS compiles to, you can use the YS CLI binary ys to run:

$ ys --compile file.ys
(let
 [names-url "https://raw.githubusercontent.com/dominictarr/random-name/master/first-names.json"
  name-list (json/load (curl names-url))]
 (%
  "name" (first (shuffle name-list))
  "aka" (rand-nth name-list)
  "age" (_& 'num (mul+ 2 3 7))
  "color" (_& 'hue (rand-nth (qw red green blue yellow)))
  "title" (str (_** 'num) " shades of " (_** 'hue) ".")))

Rust Usage

Create a new Rust project:

$ cargo new --bin prog
$ cd prog

Add the file src/main.rs:

use std::fs::File;
use std::io::prelude::*;
use yamlscript::YAMLScript;

fn main() -> std::io::Result<()> {
    let mut file = File::open("file.ys")?;
    let mut input = String::new();
    file.read_to_string(&mut input)?;
    let ys = YAMLScript::new().unwrap();
    let data = ys.load::<serde_json::Value>(&input).unwrap();
    println!("{data:?}");
    Ok(())
}

Add file file.ys:

!YS-v0:

name =: "World"

foo: [1, 2, ! inc(41)]
bar:: load("other.yaml")
baz:: "Hello, $name!"

Add file other.yaml:

oh: Hello

Run:

$ curl https://yamlscript.org/install | bash
$ cargo add yamlscript
$ cargo add serde_json
$ cargo run
    Finished dev [unoptimized + debuginfo] target(s) in 0.02s
     Running `target/debug/prog`
Object {"bar": Object {"oh": String("Hello")}, "baz": String("Hello, World!"), "foo": Array [Number(1), Number(2), Number(42)]}

Installation

You can install this module like any other Rust module:

cargo add yamlscript

but you will need to have a system install of libys.so.

One simple way to do that is with:

curl https://yamlscript.org/install | bash

Note: The above command will install the latest version of the YAMLScript command line utility, ys, and the shared library, libys.so, into ~/.local/bin and ~/.local/lib respectively.

See https://yamlscript.org/doc/install/ for more info.

See Also

• YS Web Site

• YS Blog

• YS Source Code

• YS Samples

• YS Programs

• YAML

• Clojure

Authors

• Ingy döt Net
• Ethiraric

License & Copyright

Copyright 2022-2025 Ingy döt Net ingy@ingy.net

This project is licensed under the terms of the MIT license. See LICENSE for more details.