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Initial release of Subscript

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Joined: 2010-02-07,
User offline. Last seen 34 weeks 1 day ago.

I am "finally" happy to announce the initial release of Subscript: an
extension of Scala with a theory named Process Algebra.
Subscript aims to ease event-driven and concurrent programming. You
can build so called "scripts" with sequences, choices, parallelism and
other kinds of compositions, operating on several kinds of actions.
These actions may execute normal Scala code, or handle events, or
execute code in a new thread or in the GUI thread. Concurrency in
Subscript is often lightweight, so without threading, like in the
Actor model.
Application areas are: text parsing, GUI controllers (which happen to
be much like parsers) and discrete event simulations.

A complete Subscript implementation will contain at least a compiler
and a Subscript Virtual Machine (SVM). The compiler would be a
extension of a Scala compiler. It will internally translate typical
Subscript items to specific Scala methods and other features, in a
form that is for the time being called "Internal Script
Language" (ISL). The "old part" of the compiler then generates the
usual byte code for these features.

This initial release is meant for people interested in programming
languages; it is not suitable yet for application developers. The aim
of this immature release is to raise interest to participate in
further development of the compiler and SVM. I would also welcome
comments and suggestions on the Scala code that I wrote; I am still in
the process of learning Scala (but it rocks; I don't want to go back
to Java and C# any more). No work has been done on the compiler yet.
Compilation to ISL is done by hand. There are 3 sample applications
that indicate how compilation should be done; it is fairly

The SVM code is "don't worry, be crappy" quality. Some basic tracing
functionality is provided. The 3 sample applications are the only
tested applications, at the moment. Many language features that are
not used in the sample applications, will not work. I already included
100% untested code so that it gives an idea what the good code should

The project site is It has more
sample applications, that I intend to get working during the next few
weeks. I also try to explain Process Algebra there, and how I added it
onto Scala. And there is a White Paper.

In April 2011 I gave a guest lecture and a workshop at Amsterdam
University (where Process Algebra was invented, 30 years ago) for the
master's course Thread Algebra. I discussed Subscript and a
predecessor language that extends Java. The Google code site has the
Powerpoint presentation, and a link to the student assignments used in
the work shop.

I am personally very happy with the combination of Scala and Process
Algebra. I like the concise function definitions using an equals sign
in Scala; this combines well with the Process Algebra style of
definitions. I hope many of you will like Subscript, too, and that
some of you will participate in the project at Google Code.

Copyright © 2012 École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland