https://github.com/yaml/yamlscript-lua
https://github.com/yaml/yamlscript-lua
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- Host: GitHub
- URL: https://github.com/yaml/yamlscript-lua
- Owner: yaml
- License: mit
- Created: 2025-07-10T22:59:32.000Z (11 months ago)
- Default Branch: main
- Last Pushed: 2025-07-11T14:36:04.000Z (11 months ago)
- Last Synced: 2025-07-18T06:51:15.218Z (11 months ago)
- Language: Lua
- Size: 6.84 KB
- Stars: 0
- Watchers: 0
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
YAMLScript
==========
Add Logic to Your YAML Files
## Quick Start
This library lets you load YAML files that may or may not contain
[YAMLScript](https://yamlscript.org) functional programming logic.
You can use it as a drop-in replacement for your current YAML loader.
Here's an example `config.yaml` that makes use of YAMLScript functions.
```yaml
# config.yaml with YAMLScript:
!ys-0:
# Define variables
db-host =: ENV.DB_HOST || 'localhost'
db-port =: ENV.DB_PORT || 5432
deploy =: ENV.DEPLOYMENT || 'dev'
:when deploy !~ /^(dev|stage|prod)/:
die: |
Invalid deployment value '$deploy'.
Must be one of: dev | stage | prod
# Normal YAML data
description: Dynamic application configuration
# Dynamic data values
database:
host:: db-host
port:: db-port:num
name:: "app_$deploy"
# Import external data
features:: load('common.yaml').features
# Use logic and conditions
cache:
# Variable scoped to this mapping
enabled =: deploy == 'production'
directory: .cache
enabled:: enabled
limit: 100
# Conditional key/value pairs
:when enabled::
limit:: 1000
ttl:: 60 * 60 # 3600
```
## What is YAMLScript?
YAMLScript is a functional programming language that can be embedded in YAML.
Its syntax is 100% YAML so files that embed it are still valid YAML files.
The YAMLScript project provides YAML loader libraries for many programming
languages.
They can be used to load any YAML config files properly, whether or not they
contain functional programming logic.
It's perfect for:
* **Configuration files** that need logic, variables, and dynamic values
* **Data transformation** with built-in functions for JSON, YAML, and text
processing
* **Templating** with powerful string interpolation and data manipulation
* **Scripting** as a complete functional programming language
## Key Features
* **Drop-in YAML replacement** – Works with your existing YAML files
* **Variables & functions** – Define and reuse values throughout your files
* **External data loading** – Import JSON, YAML, or data from URLs
* **Conditional logic** – Use if/then/else and pattern matching
* **Data transformation** – Built-ins for transforming & manipulating data
* **String interpolation** – Embed expressions/variables directly in strings
* **No JVM required** – Runs as a native library despite compiling to Clojure
## How It Works
YAMLScript extends YAML with a simple, elegant syntax:
```yaml
# file.yaml
!ys-0: # Enable YAMLScript
name =: 'World' # Variable assignment
nums =:: [1, 2, 3] # Any YAML value
# Literal YAML with ':'
a key: a value
# Evaluated expressions with '::'
message:: "Hello, $name!"
sum:: nums.reduce(+)
timestamp:: now():str
```
You can load this file from a program as described below, or you can use the
`ys` YAMLScript binary to load the file from the command line:
```bash
$ ys -Y file.yaml
a key: a value
message: Hello, World!
sum: 6
timestamp: '2025-09-14T22:35:42.832470203Z'
```
Under the hood, YAMLScript compiles YAML to Clojure and evaluates it, giving
you access to a rich functional programming environment.
## Lua Usage
Use `yamlscript` as a drop-in replacement for your current YAML loader:
```lua
-- program.lua
local yamlscript = require("yamlscript")
local ys = yamlscript.new()
-- Load from file
local file = io.open("config.yaml", "r")
local input = file:read("*a")
file:close()
local config = ys:load(input)
print(config)
```
## Installation
Install YAMLScript for Lua and the `libys.so` shared library:
```bash
# Install dependencies
luarocks install cffi-lua
luarocks install lua-cjson
# Install shared library
curl -sSL https://yamlscript.org/install | bash
# Add to LUA_PATH
export LUA_PATH="$(pwd)/lib/?.lua;;"
```
See for more info.
### Requirements
* Lua 5.1 or higher
* cffi-lua library
* lua-cjson library
## See Also
* [YAMLScript Web Site](https://yamlscript.org)
* [Learn YAMLScript](https://exercism.org/tracks/yamlscript)
* [YAMLScript Blog](https://yamlscript.org/blog)
* [YAMLScript Source Code](https://github.com/yaml/yamlscript)
* [YAMLScript Programs](https://rosettacode.org/wiki/Category:YAMLScript)
* [YAML](https://yaml.org)
* [Clojure](https://clojure.org)
## Authors
## Authors
* Ingy döt Net
## License & Copyright
Copyright 2022-2025 Ingy döt Net
This project is licensed under the terms of the `MIT` license.
See [LICENSE](https://github.com/yaml/yamlscript/blob/main/License) for more
details.