YAMLScript

Program in YAML

About YAMLScript

YAMLScript is a functional programming language with a stylized YAML syntax.

YAMLScript can be used for:

• Writing new programs and applications
  • Run with ys file.ys
  • Or compile to binary with ys -C file.ys
• Writing reusable shared libraries
  • Bindable to almost any programming language
• Using as a YAML loader module in many programming languages
  • Plain / existing YAML files
  • YAML files with new functional magics

Run or Load?

YAMLScript programs can either be "run" or "loaded". When a YAMLScript program is run, it is executed as a normal program. When a YAMLScript program is loaded, it evaluates to a JSON-model data structure.

Most existing YAML files in the wild are already valid YAMLScript programs. If you have a valid YAML (1.2 Core Schema) file that doesn't use custom tags, and loads to a value expressible in JSON, then it is a valid YAMLScript program. YAMLScript's load operation will evaluate that file exactly the same in any programming language / environment.

These existing YAML files obviously can't use YAMLScript's functional programming features since that would be ambiguous. For example, what is the JSON value when "loading" this YAMLScript program?

foo: inc(41)

Is it {"foo": "inc(41)"} or {"foo": 42}?

YAMLScript programs must start with a special YAML tag !yamlscript/v0 to indicate that they have functional capabilities.

!yamlscript/v0/data
foo:: inc(41)

Note: The /v0 in the tag indicates the YAMLScript API version. This is so that future versions of YAMLScript can run programs written to an older API version, and also so that older versions of YAMLScript don't try to run programs written to a newer API version.

Using YAMLScript

There are two primary ways to use YAMLScript:

• Using the ys command line runner / loader / compiler
• Using a YAMLScript library in your own programming language

The ys command line tool is the easiest way to get started with YAMLScript. It has these main modes of operation:

• ys <file> - Run a YAMLScript program
• ys --run <file> - Same as above but explicit
• ys --load <file> - Load a YAMLScript program
• ys --compile <file> - Compile a YAMLScript program to Clojure
• ys --eval '<expr>' - Evaluate a YAMLScript expression string
• ys --repl - Start an interactive YAMLScript REPL session
• ys --help - Show the ys command help

You can also use YAMLScript as a library in your own programming language. For example, in Python you can use the yamlscript module like this:

import yamlscript
ys = yamlscript.YAMLScript()
text = open("foo.yaml").read()
data = ys.load(text)

Supported Operating Systems

YAMLScript is supported on these operating systems:

• Linux
• macOS
• Windows (work in progress)

YAMLScript is supported on these architectures:

• Intel/AMD (x86_64)
• ARM (aarch64)

For now other systems cannot be supported because ys and libyamlscript are compiled by GraalVM's native-image tool, which only supports the above systems.

Supported Programming Language Bindings

YAMLScript wants to be the best YAML loader for both static and dynamic YAML usage in every programming language where YAML is used.

It will have the same API, same features, same bugs and same bug fixes in every language, giving you a great and consistent YAML experience everywhere.

At this early stage, YAMLScript has bindings for these programming languages:

• Perl
• Python
• Raku
• Ruby
• Rust

Is YAMLScript a Lisp?

Even though YAMLScript often has the look of an imperative programming language, it actually is just a (YAML based) syntax that compiles to Clojure code. The resulting Clojure code is then run by a native-machine-code Clojure runtime called Small Clojure Interpreter (SCI).

Clojure is a functional programming language with its own Lisp syntax. Therefore it is fair to say that YAMLScript is a (functional) Lisp, even though it commonly doesn't look like one syntactically.

Typically Clojure produces Java bytecode that is run on the JVM, but for YAMLScript there is no Java or JVM involved. In testing so far, YAMLScript programs tend to run as faster or faster than equivalent Perl or Python programs.

For getting started with YAMLScript, you don't need to know anything about Lisp or Clojure. You can use it with as much or as little Lisp-ness as you want; the syntax is quite flexible (and even programmable!). As your YAMLScript programming requirements grow, you can rest assured that you have the full power of Clojure at your disposal.

Try the YAMLScript ys Command

You can try out the latest version of the ys command without actually "installing" it.

If you run this command in Bash or Zsh:

. <(curl -sSL yamlscript.org/try-ys)

it will install the ys command in a temporary directory (under /tmp/) and then add the directory to your current PATH shell variable.

This will allow you to try the ys command in your current shell only. No other present or future shell session will be affected.

Try it out!

Installing YAMLScript

At the moment, the best way to install YAMLScript is to build it from source, but see the section "Installing YAMLScript Releases" below.

This is very easy to do because the YAMLScript build process has very few dependencies:

• bash (your interactive shell can be any shell)
• curl
• git
• make
• zlib-dev (need this installed on Linux)

To install the ys command line tool, and libyamlscript shared library, run these commands:

git clone https://github.com/yaml/yamlscript
cd yamlscript
make build
sudo make install

The make install command will install ys and libyamlscript to /usr/local/bin and /usr/local/lib respectively, by default. This means that you will need to run make install with sudo or as root. To install to a different location, run make install PREFIX=/some/path.

Notes:

• make install triggers a make build if needed, but...
• You need to run make build not as root
• The build can take several minutes (native-image is slow)
• If you install to a custom location, you will need to add that location to your PATH and LD_LIBRARY_PATH environment variables

Installing YAMLScript Releases

YAMLScript now ships binary releases for some platforms here.

To install a latest release for your machine platform, try:

$ curl https://yamlscript.org/install | PREFIX=~/.local bash

Make sure ~/.local/bin is in your PATH environment variable.

The default PREFIX is /usr/local, which likely requires sudo bash to run the above command.

You can use the following environment variables to control the installation:

• PREFIX=... - The directory to install to. Default: /usr/local
• VERSION=... - The YAMLScript version to install. Default: 0.1.37
• BIN=1 - Only install the PREFIX/bin/ys command line tool.
• LIB=1 - Only install the PREFIX/lib/libyamlscript shared library.
• DEBUG=1 - Print the Bash commands that are being run.

Installing a YAMLScript Binding for a Programming Language

YAMLScript ships its language binding libraries and the libyamlscript.so shared library separately.

Currently, each binding release version requires an exact version of the shared library, or it will not work. That's because the YAMLScript language is still evolving quickly.

The best way to install a binding library is to use your programming language's package manager to install the latest binding version, and the YAMLScript installer to install the latest shared library version.

So for Python you would:

pip install yamlscript
curl https://yamlscript.org/install | sudo LIB=1 bash

The Perl installation process can automatically install the shared library, so you can just do:

cpanm YAMLScript

Eventually, the YAMLScript binding installation process will become simpler and more consistent across all languages.

The YAMLScript Repository

The YAMLScript source code repository is a mono-repo containing:

• The YAMLScript compiler code
• The YAMLScript shared library code
• A YAMLScript binding module for each programming language
• The YAMLScript test suite
• The YAMLScript documentation
• The yamlscript.org website (with docs, blog, wiki, etc)

make It So

The YAMLScript repository uses a Makefile system to build, test and install its various offerings. There is a top level Makefile and each repo subdirectory has its own Makefile. When run at the top level, many make targets like test, build, install, clean, distclean, etc will invoke that target in each relevant subdirectory.

Given that this repository has so few dependencies, you should be able to clone it and run make targets (try make test) without any problems.

Contributing to YAMLScript

To ensure that YAMLScript libraries work the same across all languages, this project aims to have a binding implementation for each programming language.

If you would like to contribute a new YAMLScript binding for a programming language, you are encouraged to submit a pull request to this repository.

See the YAMLScript Contributing Guide for more details.

YAMLScript Resources

Note: The documentation linked to below is out of date, but should give you a decent idea of what YAMLScript is about. It will be rewritten soon.

• The YAMLScript Blog
• Example YAMLScript Programs on RosettaCode.org
• An early YAMLScript Presentation Video
• Old Perl YAMLScript Implementation Documentation (Out of date but informative)

Authors

• Ingy döt Net - Creator / Lead
• Ven de Thiel - Language design
• tony-o - Raku
• Ethiraric - Rust
• José Joaquín Atria - Perl
• Delon R.Newman - Ruby

Copyright and License

Copyright 2022-2024 by Ingy döt Net

This is free software, licensed under:

The MIT (X11) License