Add Logic to Your YAML Files

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."
}

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) ".")))

File prog.lua:

local yamlscript = require("yamlscript")
local ys = yamlscript.new()
local input = io.open('file.ys'):read('*a')
local data = ys:load(input)
print(data)

File file.ys:

!YS-v0:

name =: "World"

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

File other.yaml:

oh: Hello

Run:

$ lua prog.lua
{foo={1,2,42}, bar={oh="Hello"}, baz="Hello, World!"}

This Lua binding requires:

1. Standard Lua 5.1+ (not LuaJIT)
2. The cffi-lua library for FFI capabilities
3. The cjson library for JSON parsing
4. A system install of libys.so

To install the dependencies:

# Install Lua (if not already installed)
sudo apt-get install lua5.4

# Install LuaRocks (if not already installed)
sudo apt-get install luarocks

# Install required Lua libraries
luarocks install cffi-lua
luarocks install lua-cjson

# Install libys shared library
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.

To use the binding, add the lib/ directory to your LUA_PATH:

export LUA_PATH="$(pwd)/lib/?.lua;;"

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

• YS Web Site
• YS Blog
• YS Source Code
• YS Samples
• YS Programs
• YAML
• Clojure

• Ingy döt Net [email protected]

Copyright 2022-2025 Ingy döt Net [email protected]

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