RapydScript

For those who prefer Python over JavaScript and think CoffeeScript feels more like Perl

Background

• Started using Pyjamas because I was reluctant to learn JS
• Wrote an image-recognition drawing app (20k SLOCs)
• Realized Pyjamas/GWT doesn't scale and JS is not so bad
• Still had 20k lines of Python code to port
• Wrote a porting tool based on PyvaScript
• Realized that I liked this pseudo-language more than JS
• Added more features to it, others started following it
• Rewrote the core using UglifyJS2 as inspiration/base

What's wrong with JavaScript?

• It's not Python

What's wrong with JavaScript?

• It prefers global scope
• Its class implementation is counter-intuitive
• Everything is an object (typeof hell)
• Funky equality ("0" == false, arrays never equal)
• Easy to shoot yourself in the foot

What's right with JavaScript?

• Duck typing
• Everything is an object (anonymous functions, callbacks)
• Can run on the client and on the server
• Can access the DOM
• Easy to tinker after deployment

What's a Python guy to do?

• Suck it up and learn JavaScript
• Suck it up and learn CoffeeScript
• Learn RapydScript

What's wrong with CoffeeScript?

• Poor conventions leave room for ambiguity
• Even easier to shoot yourself in the foot than with JS
• It's more like Ruby/Perl than Python

Poor Conventions

In English, a comma is a more significant delimiter than a space

Poor Conventions

CoffeeScript

JavaScript

doSomething 1,
  2
  3
  4

doSomething(1, 2, 3, 4);

doSomething 1,
2
3
4

doSomething(1, 2);
3;
4;

doSomething 1,
  2
    3
   4

doSomething(1, 2, 3, 4);

Foot Shooting 101

Foot Shooting 101

Another implicit return victim:

nextState = off
totalClicks = 0
$ ->
    #Count how many button clicks there have been
    $('form').submit ->
        totalClicks++
        $('#total').text totalClicks
        false
    
    #Toggle when the toggle button is clicked
    $('#btn').click ->
        $('#state').text if nextState then "On" else "Off"
        nextState = !nextState

More like Ruby than Python

• Implicit returns
• Cool shortcut operators (->, =>, var?, @)
• Optional parentheses, commas, brackets
• More than one way to do things (until, unless, yes, on, true)

Why RapydScript?

• Combines clarity of Python with compatibility of JS
• Favors Pythonic design patterns
• Prevents bad JS habits and bugs ('var', 'new', 'this', etc.)
• Minimizes context switch for Python developers
• Full compatibility with all JS features and environments

RapydScript Example

class Rectangle:
    def __init__(self, w=1, h=1):
        self.width = w
        self.height = h
        
    def getArea(self):
        return self.width*self.height

    @staticmethod
    def isRectangle(object):
        return isinstance(object, this)
    
a = Rectangle(5, 10)
a.getArea() == Rectangle.getArea(a)
print(Rectangle.isRectangle(a))

RapydScript Example

function _$rapyd$_print() {
    var args, output;
    args = [].slice.call(arguments, 0);
    output = JSON.stringify(args);
    if ("console" in window) console.log(output.substr(1, output.length-2));
}
function Rectangle() {
    this.__init__.apply(this, arguments);
}
Rectangle.prototype.__init__ = function __init__(w, h){
    var self = this;
    if (typeof w === "undefined") w = 1;
    if (typeof h === "undefined") h = 1;
    self.width = w;
    self.height = h;
};
Rectangle.prototype.getArea = function getArea(){
    var self = this;
    return self.width * self.height;
};
Rectangle.isRectangle = function isRectangle(object){
    return object instanceof this;
};

a = new Rectangle(5, 10);
a.getArea() === Rectangle.prototype.getArea.call(a);
_$rapyd$_print(Rectangle.isRectangle(a));

Feature Set

• Inverted variable scope
• Classes and classical inheritance
• Modules, namespaces and imports
• Python standard library (makes porting/reuse easier)
• Code that makes errors more obvious
• Pythonic syntax sugar

RapydScript in the Wild

• GlowScript
• NodeBox
• salvatore.diodev.fr/RapydScript
• rapydscript.com examples
• rapydscript.com/try-it

Useful Tools

• github.com/atsepkov/vim-rapydscript
• github.com/tgienger/language-rapydscript
• github.com/charleslaw/RapydScript-Decompiler
• github.com/loolmeh/grunt-rapydscript
• github.com/vindarel/gulp-rapyd
• bitbucket.org/railcar88/flask-rapydscript
• github.com/traverseda/django-pipeline-rapydscript
• github.com/loolmeh/generator-rui-angular
• github.com/ivanflorentin/RapydFlux

Homework

Community

• rapydscript.com
• github.com/atsepkov/RapydScript
• groups.google.com/forum/#!forum/rapydscript