noscript

Noscript is an object-oriented, class-less programming language running on the Rubinius Virtual Machine.

It takes design ideas from JavaScript, CoffeeScript, Self, IO and our beloved Ruby.

Installing

Noscript only runs on Rubinius, so you have to install it (if you use RVM, here is how you do it). Assuming you have it installed:

rvm use rbx-head
git clone git://github.com/txus/noscript.git
cd noscript

You need to run noscript with Rubinius' 1.9 mode. Type this on your terminal:

echo "RBXOPT=-X19" >> ~/.bashrc

You can run your programs like this, pretty standard:

./bin/noscript examples/objects.ns

Or execute arbitrary code:

./bin/noscript -e "123.inspect().print()"

Use the -A and -B to show the AST representation and the generated Rubinius bytecode if you want. Fun! :)

Object Model

Noscript is prototype-based. Every object is a clone of another object with a reference to it. An object is just a collection of slots that can be assigned and retrieved. These slots can contain anything: literals, functions and other objects.

As a difference with most languages, identifiers may contain whitespace. So foo, each pair and do something awesome are all valid identifiers for local variables, object attributes or method names. Due to this, function invocations or method calls must have parens: do something awesome returns a function, whereas do something awesome() calls it. Just like JavaScript.

Object is the master object to clone from, available from the main scope.

To create your first object, type this:

greeter = Object.clone()
greeter.salute = -> name
  ("Hello %s!" % name).puts()
end
greeter.salute()

Basic data types

• [1, 2, 3]: Arrays. Iterable through #each.
• {a: 3, b: 9}: Tuples. Iterable through #each pair.
• 1: Fixnums. Duh.
• '1': Strings. You can format them: 'Hello %s' % 'world'.
• -> arg1, argN; foo(); end: Function literals.

Behavior reusability through Traits

Traits are like Ruby modules in the sense that they can be used to define composable units of behavior, but they are not included hierarchically. They are truly composable, meaning that are pieces that must either fit perfectly or the host object must provide a way for them to do it, normally resolving conflicts by explicitly redefining the conflicting methods.

Create your first trait like this:

Runnable = Trait.build("Runnable", {
  run: ->
    "Running!".puts()
  end
})

Serious = Trait.build("Serious", {
  run: ->
    "Running a serious business.".puts()
  end
})

person = Object.clone()
person.age = 20
person.uses(Runnable)

# If we did this now, Noscript would raise a trait conflict error, because
# person cannot have two traits with methods with the same names:
#
# person.uses(Serious)
#
# Instead we have to resolve the conflict defining the #run method on the host.

person.run = ->
  if @age > 30
    @Serious run()
  else
    @Runnable run()
  end
end

person.uses(Serious)

person.run()
# => Outputs "Running!"
person.age = 35
person.run()
# => Outputs "Running a serious business."

To read more about how traits work, read examples/traits.ns.

Interoperating with the Ruby world

Noscript can easily talk to Ruby thanks to its interoperativity API, and viceversa. This enables you to write nice polyglot applications in Ruby + Noscript.

To reopening a Ruby class from Noscript, just prefix the constant with the namespace Ruby, like this: Ruby.Array. This is the actual Array class. To call an arbitrary ruby method on an object, we use the special method send, which acts like ruby send:

Ruby.Array.send('name') # => "Array"

There are a couple of convenience methods that bypass the #send convention, namely #def, #include and #extend. Let's reopen Array and define a new method:

Ruby.Array.def('sum', ->
  @send('reduce', '+')
end)

Since Noscript arrays are instances of the ruby Array class, #sum should be also available to them using the #send convention:

[1,2,3].send('sum') # => 6

Defining new classes and modules

You can also define new classes and modules in the Ruby world from Noscript. This is done via Module#create and Class#create rather than #new, to avoid some naming conflicts.

This is useful if, for example, you want to develop a Rails application but want to write the model layer entirely in Noscript. Let's do this:

Ruby.Post = Ruby.Class.create(Ruby.ActiveRecord.Base, ->
  @send('validates_presence_of', 'title', 'body')

  @def('upcase_title', ->
    @send('title').send('upcase')
  end)
end)

You can also create mixins and include/extend them in your objects:

mixin = Ruby.Module.create(->
  @def('answer', ->; 42; end)
end)

Ruby.Post.include(mixin)

post = Ruby.Post.new()
post.send('answer') # => 42

Last but not least, let's use this Post model from Ruby. Imagine we had this post saved in post.ns. In our Ruby script we have to do this:

# my_script.rb
require 'activerecord'
require 'noscript'
noscript_require 'post'

post = Post.new
post.valid? # => false
post.answer # => 42

Using native Noscript objects from Ruby

Let's create a native, you know, prototype-based Noscript object and use it form a Ruby script.

# foo.ns
# We must put it somewhere where Ruby can see it. Let's store it in the
# toplevel constant Foo, what a great idea!
Ruby.Foo = Object.clone({
  name: 'John',
  age: ->
    20
  end,
  money: -> day of month
    30 - day of month
  end
})

Now the Ruby script:

# ruby_script.rb
require 'noscript'
noscript_require 'foo'

Foo.name      # => "John"
Foo.age       # => 20
Foo.money(20) # => 10

It's all CONNECTED!!!

Installing the old interpreter (AST-walker)

Before running on the Rubinius VM, Noscript was prototyped as a simple AST-walker interpreter written in pure Ruby, without any Rubinius-specific code.

If you want to check out what it was before I started the rewrite, check out the branch named "old".

The old branch is far from usable, but it's a nice example to play with.

git clone git://github.com/txus/noscript
git checkout old
cd noscript
bundle install
./bin/noscript examples/hello_world.ns
./bin/noscript examples/interop.ns
./bin/noscript examples/objects.ns
./bin/noscript examples/test_case.ns
./bin/noscript examples/traits.ns

Who's this

This was made by Josep M. Bach (Txus) under the MIT license. I'm @txustice on twitter (where you should probably follow me!).