MoonScript is a dynamic scripting language that compiles into Lua. It gives you the power of one of the fastest scripting languages combined with a rich set of features.
local Thing
do
local _parent_0 = nil
local _base_0 = {
name = "unknown"
}
_base_0.__index = _base_0
if _parent_0 then
setmetatable(_base_0, _parent_0.__base)
end
local _class_0 = setmetatable({
__init = function(self, ...)
if _parent_0 then
return _parent_0.__init(self, ...)
end
end,
__base = _base_0,
__name = "Thing",
__parent = _parent_0
}, {
__index = function(cls, name)
local val = rawget(_base_0, name)
if val == nil and _parent_0 then
return _parent_0[name]
else
return val
end
end,
__call = function(cls, ...)
local _self_0 = setmetatable({}, _base_0)
cls.__init(_self_0, ...)
return _self_0
end
})
_base_0.__class = _class_0
if _parent_0 and _parent_0.__inherited then
_parent_0.__inherited(_parent_0, _class_0)
end
Thing = _class_0
end
local Person
do
local _parent_0 = Thing
local _base_0 = {
say_name = function(self)
return print("Hello, I am", self.name)
end
}
_base_0.__index = _base_0
if _parent_0 then
setmetatable(_base_0, _parent_0.__base)
end
local _class_0 = setmetatable({
__init = function(self, ...)
if _parent_0 then
return _parent_0.__init(self, ...)
end
end,
__base = _base_0,
__name = "Person",
__parent = _parent_0
}, {
__index = function(cls, name)
local val = rawget(_base_0, name)
if val == nil and _parent_0 then
return _parent_0[name]
else
return val
end
end,
__call = function(cls, ...)
local _self_0 = setmetatable({}, _base_0)
cls.__init(_self_0, ...)
return _self_0
end
})
_base_0.__class = _class_0
if _parent_0 and _parent_0.__inherited then
_parent_0.__inherited(_parent_0, _class_0)
end
Person = _class_0
end
do
local _with_0 = Person()
_with_0.name = "MoonScript"
_with_0:say_name()
end
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 as
require "moonscript" in order to have Lua understand how to load and run any
MoonScript file.
Because it compiles right into Lua code, it is completely compatible with alternative Lua implementations like LuaJIT, and it is also compatible with all existing Lua code and libraries.
The command line tools also let you run MoonScript directly from the command line, like any first-class scripting language.
A comprehensive overview of the language can be found in the reference manual, the rest of this page serves as an overview of the language.
Overview
MoonScript provides a clean syntax using significant whitespace that avoids all the keyword noise typically seen in a Lua script. Below is a sample of some constructs found in the language.
local x = 2323
local collection = {
height = 32434,
hats = {
"tophat",
"bball",
"bowler"
}
}
my_func = function(a)
return x + a
end
print(my_func(100))
export my_func
x = 2323
collection =
height: 32434
hats: {"tophat", "bball", "bowler"}
my_func = (a) -> x + a
print my_func 100
It also adds table comprehensions, implicit return on functions, classes, inheritance, scope management statements import & export, and a convenient object creation statement called with.
local concat, insert = table.concat, table.insert
local double_args
double_args = function(...)
return (function(...)
local _accum_0 = { }
local _len_0 = 0
local _list_0 = {
...
}
for _index_0 = 1, #_list_0 do
local x = _list_0[_index_0]
_len_0 = _len_0 + 1
_accum_0[_len_0] = x * 2
end
return _accum_0
end)(...)
end
local tuples = (function()
local _accum_0 = { }
local _len_0 = 0
for k, v in ipairs(my_table) do
_len_0 = _len_0 + 1
_accum_0[_len_0] = {
k,
v
}
end
return _accum_0
end)()
import concat, insert from table
double_args = (...) ->
[x * 2 for x in *{...}]
tuples = [{k, v} for k,v in ipairs my_table]
It 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.
Installation
Installing with LuaRocks
If you're on Windows, then install the Windows binaries, otherwise the easiest way to install is to use LuaRocks.
LuaRocks can be obtained here or from your package manager.
After it is installed, run the following in a terminal:
$ luarocks install moonscript
This will provide the moon and moonc executables along with the
moonscript and moon Lua module.
Windows Binaries
Procompiled Windows binaries are available to avoid the trouble of compiling:
http://moonscript.org/bin/moonscript-0.2.3-2.zip
Extract the contents into your PATH.
Optional
If you're on Linux and use watch mode (which compiles .moon files to .lua
files as they are changed) you can install
linotify to use inotify instead of
polling.
Source
The source code to the project lives on github:
https://github.com/leafo/moonscript
Issues with the tool can be reported on the issue tracker:
https://github.com/leafo/moonscript/issues
The latest development version can be installed with the dev rockspec:
$ luarocks build http://moonscript.org/rocks/moonscript-dev-1.rockspec
Dependencies
In addition to Lua 5.1, the following Lua modules are required to run the compiler and associated tools:
- LPeg
- LuaFileSystem
- alt-getopt
- and optionally on Linux linotify
All of the required ones can be retrieved automatically using the LuaRocks installation.
Extras & Addons
Editor Support
Vim syntax and indent:
https://github.com/leafo/moonscript-vim
Textmate (and Sublime Text) syntax and indent:
https://github.com/leafo/moonscript-tmbundle
SciTE (with scintillua) syntax:
https://github.com/leafo/moonscript/tree/master/extra/scintillua
Preconfigured and packaged version of SciTE for Windows with MoonScript
support:
http://moonscript.org/scite/
Tools
Online Compiler:
http://moonscript.org/compiler/
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
exportkeyword to declare global variables,importkeyword 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 inself!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
__indexproperty - Constructor arguments can begin with
@to cause them to automatically be assigned to the object - Magic
superfunction which maps to super class method of same name in a class method withstatement lets you access anonymous object with short syntax
About
The syntax of MoonScript has been heavily inspired by the syntax of CoffeeScript. MoonScript is CoffeeScript for Lua.
MoonScript would not have been possible without the excellent tool LPeg for parsing.
