RapydScript

What is RapydScript?

RapydScript is a pre-compiler for JavaScript. The syntax is very similar to Python, but allows JavaScript as well. This project was written as a cleaner alternative to CoffeeScript. Here is a quick example of a high-performance Fibonacci function in RapydScript and the JavaScript it produces after compilation:

def memoize(f):
    memo = {}
    return def(x):
        if x not in memo: memo[x] = f(x)
        return memo[x]

@memoize
def fib(n):
    if n == 0: return 0
    elif n == 1: return 1
    else: return fib(n-1) + fib(n-2)

JavaScript:

function _$rapyd$_in(val, arr) {
    if (arr instanceof Array || typeof arr === "string") {
        return arr.indexOf(val) != -1;
    }
    return arr.hasOwnProperty(val);
}
function memoize(f) {
    var memo = {};
    return function(x) {
        if (!(_$rapyd$_in(x, memo))) {
            memo[x] = f(x);
        }
        return memo[x];
    };
}

fib = memoize(function fib(n) {
    if (n === 0) {
        return 0;
    } else if (n === 1) {
        return 1;
    } else {
        return fib(n - 1) + fib(n - 2);
    }
});

Here are just a few examples of cleaner RapydScript syntax:

| RapydScript | JavaScript | | ------------------------ | ------------------------------------------------------------------------------ | | foo = 1 | var foo = 1; | | thing in stuff | stuff.indexOf(thing) != -1 | | a < b < c | a < b && b < c | | def(a, b='foo'): | function(a, b) { if (typeof b === 'undefined') b = 'foo'; } | | array[-1] | array[array.length-1] | | array[3:5] = [7, 8, 9] | [].splice.apply(array, [3, 5-3].concat([ 7, 8, 9 ])) | | [5 to 15] | Array.apply(null, {length: 11}).map(Number.call, function(n){ return n+5; }) | | [a**2 for a in array] | // Really, really long for-loop code... | | {a: "?"} == {a: "?"} | // Bet you didn't know deep equality with no overhead was possible |

RapydScript allows to write your JavaScript app in a language much closer to Python without the overhead that other similar frameworks introduce (the performance is the same as with pure JavaScript). To those familiar with CoffeeScript, RapydScript is like CoffeeScript, but inspired by Python's readability rather than Ruby's cleverness. To those familiar with Pyjamas, RapydScript brings many of the same features and support for Python syntax without the same overhead. Don't worry if you've never used either of the above-mentioned compilers, if you've ever had to write your code in pure JavaScript you'll appreciate RapydScript. RapydScript combines the best features of Python as well as JavaScript, bringing you features most other Pythonic JavaScript replacements overlook. Here are a few features of RapydScript:

• == compiles to deep equality and uses clever optimizations to avoid performance overhead
• type inference that allows for hybrid-typing similar to TypeScript
• intelligent scoping (no need for repetitive var or new keywords)
• intelligent code optimizations based on context
• much cleaner code than native JavaScript
• optional function arguments that work just like Python (func(third='foo'))
• decorators, list comprehensions, dict comprehensions, verbose regex, starargs, kwargs, you name it
• ability to use both, Python's methods/functions and JavaScript's alternatives
• similar to above, ability to use both, Python's and JavaScript's tutorials (as well as widgets)
• classes that work and feel very similar to Python
• inheritance system that's both, more powerful than Python and cleaner than JavaScript (single inheritance w/ mixins);
• pythonic import system (you can also use require())
• support for object literals with anonymous functions, like in JavaScript
• ability to invoke any JavaScript/DOM object/function/method as if it's part of the same framework, without the need for special syntax
• it's self-hosting, the compiler is itself written in RapydScript and compiles into JavaScript

Let's not waste any more time with the introductions, however. The best way to learn a new language/framework is to dive in.

Table of Contents

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• Installation
• Community
• Compilation
• Getting Started
• Leveraging other APIs
• Anonymous Functions
• Decorators
• Function Annotations
• Hybrid and Static Typing
• Self-Executing Functions
• Chaining Blocks
• Function calling with optional arguments
• Inferred Tuple Packing/Unpacking
• Python vs JavaScript
• Loops
• Dict and List Comprehensions
• Inclusive/Exclusive Sequences
• Classes
  • External Classes
  • Method Binding
• Modules
• Exception Handling
• Scope Control
• Importing
• Regular Expressions
• ES6 Features
• Available Libraries
• Advanced Usage Topics
  • System Scripts
  • Unit Testing
  • Browser Compatibility
  • Code Conventions
    • Tabs vs Spaces
    • Object Literals vs Hashes/Dicts
    • Semi-Colons
    • Raw JavaScript
    • jQuery-wrapped Elements
    • Libraries
    • External Libraries and Classes
• Quirks

<!-- END doctoc generated TOC please keep comment here to allow auto update -->

Installation

First make sure you have installed the latest version of node.js (You may need to restart your computer after this step).

From NPM for use as a command line app:

npm install rapydscript -g

From NPM for programmatic use:

npm install rapydscript

From Git:

git clone git://github.com/atsepkov/RapydScript.git
cd RapydScript
npm link .

If you're using OSX, you can probably use the same commands (let me know if that's not the case). If you're using Windows, you should be able to follow similar commands after installing node.js and git on your system.

Community

If you have questions, bug reports, or feature requests, feel free to post them on our mailing list:
http://groups.google.com/group/rapydscript

I bundled a few demos with RapydScript itself, but several members of the community put together much better demos. If you would like to take a look at them to see what's possible with RapydScript, here are some examples:

http://www.glowscript.org/
GlowScript is a WebGL-based environment and a physics engine, originally written in Python for the desktop, the author ported it to the browser using RapydScript compiler.

http://salvatore.pythonanywhere.com/RapydScript
This includes the demos from RapydScript's examples directory, as well as a few others.

http://salvatore.pythonanywhere.com/RapydBox
This is a collection of very cool demos, showcasing RapydScript's similarity to real Python and at the same time its ability to work with other JavaScript. It relies on a JavaScript port of NodeBox (which was originally written in Python). NodeBox was ported from Python to JavaScript to allow cross-platform compatibility. Ironically, the original demos from Python version of NodeBox now work with JavaScript version of NodeBox with few changes (and sometimes none at all) by using RapydScript.

http://salvatore.pythonanywhere.com/RapydGlow
RapydScript making use of GlowScript, another project done by a member of our community

https://github.com/adousen/RapydScript-pyjTransformer An in-browser compiler that allows you to use uncompiled RapydScript files in the browser directly via script tags:

<script type="text/pyj" otype="text/jsx" src="helloworld.pyj" async="false"></script>

https://github.com/atsepkov/puzzles/tree/master/project-euler
My solutions to Project Euler challenges in RapydScript. For those unfamiliar with projecteuler.net, it's a collection of mathematical puzzles for developers testing their ability to come up with clever/efficient algorithms as well as brevity/elegance of their chosen language. While Python and Ruby are popular choices, barely any solutions are in JavaScript (probably due to the language's arcane syntax and error handling and very limited utility for mathematical challenges out of the box). RapydScript, however, does quite well - sometimes allowing for identical solution as Python, sometimes a more clever one. Execution speed is typically faster than Python, but in some cases lags behind (i.e. when Python version uses sets or optimized numpy logic).

Compilation