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Obtaining Erlang/OTP and books/articles about it

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3 Obtaining Erlang/OTP and books/articles about it

3.1  Where can I get Erlang/OTP?

Open Source Erlang/OTP can be downloaded from the open source Erlang site. The site provides full source code as well as binaries for Windows machines. This is probably the best place to go to make sure you're getting the latest version.

The Debian Distribution of GNU/Linux, and derivatives such as Ubuntu, includes various versions Erlang in different releases, under interpreters.

Precompiled ready-to-go installers for a variety of platforms are available from the Comprehensive Erlang Archive Network (CEAN). CEAN also provides dozens of Erlang applications.

For the BSDs, the 'ports' collection has up to date versions of Erlang.

Users within Ericsson can use Ericsson's internally supported version of Erlang from www.erlang.se.

3.2  What's the current version of (Open Source) Erlang?

R14B was released in September 2010. As further patches are released, the "current" version becomes R14B01, R14B02 etc. This curious version numbering scheme is also used on Ericsson mobile phones, for instance my phone is an R1F phone...

Before the R13 releases, releases were named R12B-0, R12B-1, R12B-2 etc.

Major releases typically come somewhere between 12 and 18 months apart.

Components of Erlang have their own version numbers, for instance the virtual machine in R7B-0 has version 5.0.1 (yes, this is a bit confusing; see also).

3.3  Which licence is Open Source Erlang shipped with?

The Open Source Erlang Licence is essentially the Mozilla (Netscape) Public Licence with a few modifications to make it compatible with Swedish law.

As far as I understand, this means you can obtain Erlang for free, use it to build cool systems and sell them without Ericsson coming around to charge you money. For an authoritative statement, you'll need a lawyer.

3.4  What documentation is there for Erlang?

The language itself is best described by the Language Reference Manual.

The documentation delivered with open source erlang as both man pages and html is the most up-to-date reference to both the OTP libraries and Erlang itself. On unix systems, the an easy way to read the man pages is erl -man gen_tcp .

Erlang and OTP in Action by Martin Logan, Eric Merritt and Richard Carlsson is the most recent book about Erlang, published in 2010. You can buy it from various online bookstores, or directly from the publisher.

Erlang Programming (A Concurrent Approach to Software Development) by Francesco Cesarini and Simon Thompson was published in 2009. Get it from Amazon etc or directly from the publisher.

Programming Erlang: Software for a Concurrent World (Joe Armstrong) is a book about Erlang written by one of the original inventors, published in 2007. You can buy it on paper from Amazon and other online bookstores, or directly from the publisher.

Erlang Programmation(Mickaël Rémond) is an alternative if your French is up to it, it can be ordered from the publisher or via Amazon.

Concurrent Programming in Erlang (2nd. Edition, 1993) (Armstrong, Virding, Wikström & Williams) is only of historical interest. Archaeologists can download the first half of the book from erlang.org.

Also only of historical interest: Maurice Castro's book, Erlang in Real Time (1998).

3.5  What advanced Erlang documentation is there?

The Standard Erlang spec aims to define the Erlang language. There is currently no compiler which actually implements everything exactly the way Standard Erlang specifies. This specification is quite precise; it's intended as a reference, not a bedtime read! Compiler and tool implementors will find this useful, as will advanced Erlang programmers.

Core Erlang is an effort to define an Erlang-like language which is nicer to compilers and language tools and can be automatically generated from Erlang. Erlang compilers from R10 onwards can generate Core Erlang from normal Erlang code. They can also generate .beam files from Core Erlang.

The Erlang Rationale is a short (13 page) discussion written by one of the original authors of Erlang about why some parts of Erlang became the way they are. It's a work in progress.

The proceedings from the Erlang User Conferences contain many interesting articles. The proceedings for each of the yearly conferences since 1999 are online.

The internals of the BEAM file format are described on Björn's homepage . Eventually this will/might include a description of the virtual machine's instructions. Björn also includes some benchmarks comparing different versions of the BEAM machine. You may also want to take a look at the beam_lib module.

Joe Armstrong's Thesis, Making reliable distributed systems in the presence of software errors contains a lot of interesting information, including a compact overview of the language, a number of case studies and some discussion of the language's evolution, somewhat similar to Bjarne Stroustrup's Design and Evolution of C++.

This Masters Thesis contains a good overview of some of Erlang's implementation aspects, including memory allocation (section 7).

Another Masters Thesis contains a good overview of Erlang's distribution mechanisms (Section 5).

Mnesia's internals are described on Håkan's slides

The (Ex-Ericsson) computer science laboratory has a collection of papers about Erlang-related topics.

The source-code release includes a directory with some of the internal build documentation in the subdirectory erts/emulator/internal_doc/ .

Erlang-projects has a collection of papers written at the now-defunct SERC division of RMIT.

The Trapexit wiki has a collection of HowTo documents showing how to do all manner of things from how to write a webserver in Erlang to how to write an Erlang Port program.

3.6  What documentation is there in related subjects?

The standard text about data structures in functional languages is Purely Functional Data Structures by Chris Okasaki. The parts about laziness (about half of the book) do not apply to Erlang, but are interesting nonetheless. An early version of the book is available online, the book itself is available from many online booksellers.

Structure and Interpretation of Computer Programs is a standard introductory text to functional programming. It is available both on paper and online

(Suggestions for further books to for this section are welcome. Mail the maintainer: matthias@corelatus.com.)

3.7  Is there public CVS/Git/your-favourite-vcs repository for the Erlang source?

As of R13B03 (November 2009), there is an official Git repository maintained (daily!) by the Erlang/OTP group. There is also an unofficial repository which includes history before the R13B03 release.

3.8  How can I contribute to Erlang?

When you write Erlang code you want to share, there are quite a number of ways to share it. The place to announce such things is the Erlang Questions mailing list, or, in the case of patches, the Erlang Patches mailing list. Where you put the actual code is up to you.

If your code is a correction, modification or extension to an existing part of OTP, the usual way of spreading it is via github, the wiki has instructions.

If your code is a new application or library, some common ways of distributing it are:

3.9  How can I propose changes to the language itself?

Even though Erlang is a fairly mature language with a large established code-base, changes and enhancements are still being incorporated. There is a mechanism called the Erlang Enhancement Proposal which formalises the process.

3.10  Where is Erlang discussed in the real world?

Conferences

Every year (in September or October) there is an Erlang user conference. The proceedings are archived.

In June 2008 and April 2009, the first ever commercial Erlang conferences were held in London and San Francisco. This is now a regular event with further Erlang Exchange events planned.

Academic conferences about functional programming are also attended by a few Erlang users. The Principles, Logics, and Implementations of High-Level Programming Languages usually includes an Erlang workshop. The ACM Sigplan Conference includes an Erlang workshop too.

Erlounge and User Groups

Every so often, someone puts out an invitation on erlang-questions to informally discuss Erlang over a few beers. Past Erlounges have been in Sweden (Stockholm), Scotland, the USA (Atlanta, New York, Chicago, North Carolina, Schaumburg, Seattle, SF Bay area, Arlington, Washington DC), France (Paris), China (I can't read the characters which described the location), Italy, Germany (Aachen), Poland (Krakow), New Zealand (Wellington) and others. There's a Trapexit page listing known usergroups.

3.11  Where is Erlang discussed online?

There are several mailing lists devoted to Erlang:

erlang-questions

This is intended for general discussion about Erlang. Anyone can send mail to erlang-questions@erlang.org, and anyone can subscribe.

erlang-announce

This list carries announcements about new releases of Erlang, patches, etc. All posts to erlang-announce also appear in erlang-questions.

erlang-patches

This list is for patches to the Erlang distribution. At the time of writing, it is not archived.

erlang-bugs

This list is for bug reports.

Web forums and mailing list archives

The erlang-questions list is archived on the Erlang website.

The GMANE news/mail gateway acts as both an archive and a forum-style way of using the mailing list. It has Erlang Questions and Erlang Patches.

The trapexit site also has a forum interface to the mailing list.

IRC channel

There's an IRC channel, #erlang, on irc.freenode.net

3.12  Are there any websites apart from erlang.org?

Erlang-projects aims to track Erlang use in projects.

trapexit is a grab-bag of erlang news, erlang-related forums and a bidirectional forum/mailing list gateway.

planet erlang aggregates a couple of dozen erlang-related RSS feeds.

The Ericsson site for all matters related to Ericsson-internal use of Erlang also contains information about internal training and consulting.

The mozilla dmoz has a directory of Erlang links.

3.13  Where can I find Erlang programmers/employers?

Posting a short note to erlang-questions@erlang.org is a good start, especially if the subject-line clearly identifies the post as a job request/advert.

There are several sites with a high concentration of Erlang jobs:

Several consultant groups have Erlang-certified people in Sweden, including ENEA data and Sjöland & Thyselius. erlang-solutions.com take assignments worldwide. Process-one are based in France.

If you want to be listed here, send some mail to matthias@corelatus.com.

Kontakten (Contact), an Ericsson-internal newspaper, may also be useful as it carries many job ads.