Opa Programming language

Opa Programming language

Opa is an open source programming language for developing scalable web applications.

It can be used for both client-side and server-side scripting, where complete programs are written in Opa and subsequently compiled to Nodejs on the server and JavaScript on the client, with the compiler automating all communication between the two. Opa implements strong, static typing, which can be helpful in protecting against security issues such as SQL injections and cross-site scripting attacks.

The language was first officially presented at the OWASP conference in 2010, and the source code was released on GitHub in June 2011, under a GNU Affero General Public License. Later, the license changed to the MIT license for the framework part (library) and AGPL for the compiler so that applications written in Opa can be released under any license, proprietary or open source.

Design & Features

Opa consists of a web server, a database and distributed execution engine. Code written in Opa is compiled to JavaScript using Node.js on the server side and to JavaScript using jQuery for cross-browser compatibility on the client side. The advantage of the approach compared to certain Rich Internet Application (RIA) platforms is that users are not required to install a plugin in their browser. Opa shares motivations with web frameworks, but takes a different approach. Its designers assert that this helps Opa to avoid many security issues, like SQL injections or cross-site scripting (XSS) attacks.

The core language is functional and has a static type system with type inference. Opa also provides sessions which encapsulate an imperative state and communicate using message passing, similar to Erlang processes. Opa provides many structures or functions that are common in web development, as first-class objects, for instance HTML and parsers, based on Parsing Expression Grammars.Because of this adhesion between the language and web-related concepts, Opa is not intended for non-web applications (for instance desktop applications)^.

The 0.9.0 release in February 2012 introduced database mapping technology for the non-relational, document-oriented database MongoDB, similar to object-relational mapping. The 1.1.0 release in February 2013 also added support for PostgreSQL, paving the way for the support of several SQL databases.

Examples

Hello world

The traditional Hello world program, producing a web server that serves a static page with "Hello, web!" as its content, can be written in Opa as:

Server.start(Server.http,

  { title: "Hello"

  , page: function() { <h1>Hello, web!</h1> }

  }

)

It can be compiled to a stand-alone executable JS file with:

$ opa hello_web.opa

Running the resulting executable JS file launches the web application:

$ ./hello_web.js

Top 10 Reasons to Develop with Opa

1. One Language to Rule Them All

Write simultaneously the frontend and backend code, in the same language, within the same module. Even better: the Opa Slicer automates the calls between client and server. No more manually written AJAX calls or value serialization!

And when auto is not enough, add hints to the code to enforce client or server-side, privacy, synchronous or asynchronous.

2. Access All JavaScript Libraries

Opa generates and is fully compatible with standard JavaScript code.

Reuse tons of existing JavaScript libraries and frameworks, such as JQuery which is by default part of the standard library.

3. Robust Runtime

Opa generates JavaScript on the server too, using Node.js and MongoDB.

Applications built with Opa can be deployed in most cloud straightforwardly and scaled up or down easily.

4. Database Automation

Database queries are also written directly with Opa.

Opa currently supports both the SQL database PostgreSQL and NoSQL databases MongoDB and CouchDB. More databases are planned for future releases.

Opa provides many unique advanced operators and automates the database queriesfor maximal productivity.

5. Typechecker

Opa unique feature is its advanced typechecker that automatically verifies your application code, looking for bugs and inconsistencies, and crunching debugging time.

The Opa Type Checker was designed to bring static verifications to dynamic programming experience. Type checking is incredibly fast and features type inference: Application code stays lean and clean.

6. Truly Non-Blocking

Modern applications use a lot of asynchronous calls. Dealing with callbacks manually can be painful, and failing to do so properly blocks the application runtime.

To make asynchronous programming easy without blocking the application, Opa-generated JavaScript code uses smart continuations.

In the following example the Opa compiler automatically takes care of everything.

7. MVC Support

Opa support MVC (Model-View-Controller) programming and provides a scaffolding mechanism to get started instantly.

Just minutes away from creating a real application.

8. HTML5 Native Support

Opa is built for the modern web. HTML5 fragments can be inserted directly. No more messing with single and double quotes!

CSS(3) elements including selectors are also easier than ever to use.

9. Powerful Syntax

Opa is JavaScript on steroids with many syntax and feature enhancements.

Database, types, pointers, autoclose, higher-order functions, etc. The list is way too long to fit here. Find it on the reference card.

10. Power Rows

The core of Opa uses Power Rows: A powerful, statically-typed, extension of JavaScript objects.

Power Rows is one of the features that makes Opa safe and fun at the same time.

For more information, please visit, www.programmingyan.com