MoonScript

MoonScript is a programmer friendly language that compiles into Lua. It gives you the power of the fastest scripting language combined with a rich set of features:

• Provides a clean syntax using significant whitespace that avoids all the keyword noise typically seen in a Lua script.

• Adds table comprehensions, implicit return on functions, classes, inheritance, scope management statements import & export, and a convenient object creation statement called with.

• Can be loaded directly from a Lua script without an intermediate compile step. It even knows how to tell you where errors occurred in the original file when they happen.

Creating an instance of a class and calling a method:

 class Thing
   name: "unknown"
 
 class Person extends Thing
   say_name: -> print "Hello, I am", @name
 
 with Person!
   .name = "Moonscript"
   \say_name!

MoonScript can either be compiled into Lua and run at a later time, or it can be dynamically compiled and run using the moonloader. It's as simple require "moon" in order to have Lua understand how to load and run any MoonScript file.

The command line tools also let you run MoonScript directly from the command line, like any first-class scripting language.

Installation

Installing with LuaRocks

The easiest way to install is to use Lua rocks and the provide rockspec.

LuaRocks can be obtained here or from your package manager.

After it is installed, run the following in a terminal:

~> wget https://raw.github.com/leafo/moonscript/master/moonscript-dev-1.rockspec
~> luarocks install moonscript-dev-1.rockspec

This will provide the moon and moonc tools along with the moonscript Lua module.

Optional

If you are on Linux and want to run watch mode, which compiles .moon files to .lua files as they are changed, you can install linotify.

Learning

Read the reference manual.

Command Line Use

Two tools are installed with MoonScript, moon and moonc. moonc is used for transforming MoonsScript code into a Lua file. It takes a list of files, compiles them all, and creates the associated .lua files in the same directories.

moon

moon can be used to run MoonsScript files directly from the command line, without needing a separate compile step. All MoonsScript files are compiled in memory as they are run.

~> moon my_script.moon

Any MoonScript files that are required will also be compiled and run automatically.

When an error occurs during runtime, the stack trace is rewritten to give line numbers from the original .moon file.

If you want to disable error rewriting, you can pass the -d flag. A full list of flags can be seen by passing the -h or --help flag.

moonc

moonc is used for transforming a MoonsScript file into a Lua file. It takes a list of files, compiles them all, and creates the associated .lua files alongside the .moon files.

~> moonc my_script1.moon my_script2.moon ...

You can control where the compiled files are put using the -t flag, followed by a directory.

moonc can also take a directory as an argument, and it will recursively scan for all MoonScript files and compile them.

Combined with linotify on linux, the -w flag can be used to watch all files that match the given search path for changes, and then compile them only when required.

A full list of flags can be seen by passing the -h or --help flag.

Overview of Differences & Highlights

A more detailed overview of the syntax can be found in the documentation.

• Whitespace sensitive blocks defined by indenting
• All variable declarations are local by default
• export keyword to declare global variables, import keyword to make local copies of values from a table
• Parentheses are optional for function calls, similar to Ruby
• Fat arrow, =>, can be used to create a function with a self argument
• @ can be prefixed in front of a name to refer to that name in self
• ! operator can be used to call a function with no arguments
• Implicit return on functions based on the type of last statement
• ':' is used to separate key and value in table literals instead of =
• Newlines can be used as table literal entry delimiters in addition to ,
• \ is used to call a method on an object instead of :
• +=, -=, /=, *=, %= operators
• != is an alias for ~=
• Table comprehensions, with convenient slicing and iterator syntax
• Lines can be decorated with for loops and if statements at the end of the line
• If statements can be used as expressions
• Class system with inheritance based on metatable's __index property
• Constructor arguments can begin with @ to cause them to automatically be assigned to the object
• Magic super function which maps to super class method of same name in a class method
• with statement lets you access anonymous object with short syntax

Dependencies

The following are used in MoonScript:

• Lua 5.1
• LPeg
• LuaFileSystem
• alt-getopt
• and optionally on Linux linotify

License (MIT)

Copyright (C) 2011 by Leaf Corcoran

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.