Implementations and Ports of Erlang

Table of Contents

• What is Erlang
  • Top of chapter
  • In a nutshell, what is Erlang?
  • What is OTP?
  • What sort of applications is Erlang particularly suitable for?
  • What sort of problems is Erlang not particularly suitable for?
  • Who uses Erlang for product development?
  • Who uses Erlang for research and teaching?
  • Can I get commercial support for Erlang?
• Questions about this FAQ
  • Top of chapter
  • Where can I get the latest version of the FAQ?
  • What's new?
  • Where do I ask questions which are not answered in this FAQ?
  • The answer to question 2.4 is wrong!
  • Disclaimer/Distribution
• Obtaining Erlang/OTP and books/articles about it
  • Top of chapter
  • Where can I get Erlang/OTP?
  • What's the current version of (Open Source) Erlang?
  • Which licence is Open Source Erlang shipped with?
  • Where is the Erlang documentation?
  • Which book about Erlang should I read?
  • What advanced Erlang documentation is there?
  • What documentation is there in related subjects?
  • Is there public repository for the Erlang source?
  • How can I contribute to Erlang?
  • How can I propose changes to the language itself?
  • How do I report a bug?
  • Where is Erlang discussed in the real world?
  • Where is Erlang discussed online?
  • Where can I find Erlang programmers/employers?
• Getting Started
  • Top of chapter
  • How long does it take to learn Erlang?
  • How can I learn Erlang?
  • What does "hello world" look like?
  • How do I quit the Erlang shell?
  • Why does Erlang print "ok" after my program's output?
• How do I...
  • Top of chapter
  • ...compare numbers?
  • ...represent a text-string?
  • ...convert a string to lower case?
  • ...convert a text string representation of a term to a term?
  • ...use unicode/UTF-8?
  • ...destructively update data, like in C
  • ...run an Erlang program directly from the unix shell?
  • ...communicate with non-Erlang programs?
  • ...write a unix pipe program in Erlang?
  • ...communicate with a DBMS?
  • ...decode binary Erlang terms
  • ...decode Erlang crash dumps
  • ...estimate performance of an Erlang system?
  • ...measure performance of an Erlang system?
  • ...measure memory consumption in an Erlang system?
  • ...estimate productivity in an Erlang project?
  • ...use multiple CPUs (or cores) in one server?
  • ...run distributed Erlang through a firewall?
  • ...distribute the Erlang programs I write to my friends/colleagues/users?
  • ...write to standard error (stderr)?
• Erlang Libraries
  • Top of chapter
  • What's in the OTP libraries?
  • Is there a collection of data structures, e.g. balanced trees?
  • Is there a serial port driver for Erlang?
  • Is there a toolkit for building GUIs?
  • I've written an application/library. How do I package it so others can use it?
  • I've written a library to handle XYZ. How do I get it into the standard Erlang distribution?
• Erlang Tools
  • Top of chapter
  • Is there a pretty printer for Erlang?
  • Is there an erlang formatter for CI?
  • Where is the source for LEEX (the erlang lexer)?
  • Is there a diagram tool specifically for Erlang?
  • What code testing tools and suites exist for and in Erlang/OTP?
  • Is there a way to benchmark an Erlang implementation?
  • Does anyone have a magic file for Erlang?
  • Which IDE should I use for Erlang development?
  • Are there Erlang Coding Guidelines?
  • What refactoring tools are there for Erlang
  • What static code analysis tools are there?
  • Is there a "reverse compiler" for BEAM files?
• Implementations and Ports of Erlang
  • Top of chapter
  • Open Source Erlang
  • What Experimental, Research and Historical Implementations are there?
  • Which version of Erlang am I running?
  • What operating systems does Erlang run on?
  • What implementations of the Erlang Virtual Machine are there?
  • Can Erlang be compiled under Microsoft Windows?
  • How can I cross-compile Erlang?
  • Is Erlang small enough for embedded systems?
• Troubleshooting, Problems and 'Gotchas'
  • Top of chapter
  • Why can't I write a = 3 (badmatch)?
  • Why can't I change the value of a variable?
  • Why do lists of numbers get printed incorrectly?
  • Why can't I call arbitrary functions in a guard?
  • Why can't I use "or" in a guard?
  • Why does 'catch' give me a syntax error?
  • What is a sticky directory?
  • Why won't my distributed Erlang nodes communicate?
  • When distribution won't work
  • Avoiding DNS
  • Why does my application die every second time I load new code into it?
  • Why can't I open devices (e.g. a serial port) like normal files?
  • Why doesn't the stack backtrace show the right functions for this code:
  • What do I do if I get an error when compiling Open Source Erlang?
  • Why do errors in the shell kill other processes?
  • Why do I get incorrect answers for floating-point operations?
• Academic and Historical Questions
  • Top of chapter
  • Why is Erlang called "Erlang"?
  • Who invented Erlang?
  • Where does Erlang syntax come from?
  • Why is Ericsson giving away Erlang?
  • What does soft realtime mean?
  • How did the first Erlang compiler get written?
  • Erlang Syntax and Semantics Details
  • Is the order of message reception guaranteed?
  • If I send a message, is it guaranteed to reach the receiver?
  • What limits does Erlang have?
  • Do funs behave during a code change?
  • Examples of bound funs causing surprises
  • Is it just me, or are records ugly?
  • Can a process receive messages with varying priorities?
  • What's the history of static type checking in Erlang?
  • How does type checking in Erlang compare to Java/Python/C/C++/Haskell?
  • What's Erlang's relation to 'object oriented' programming?
  • How are strings implemented and how can I speed up my string code?
  • How does the Garbage Collector (GC) work?
  • Can I exploit knowledge about my program to make the GC more efficient?
  • Could the Java Virtual Machine be used to run Erlang?
  • Is it possible to prove the correctness of Erlang programs?
  • I've heard it's a bad idea to program defensively in Erlang. Why?
• Mnesia Database Questions
  • Top of chapter
  • What is Mnesia good at?
  • What is Mnesia not so good at?
  • Is Mnesia good for storing blobs?
  • Is there an SQL interface for mnesia?
  • How much data can be stored in Mnesia?

8 Implementations and Ports of Erlang

8.1  Open Source Erlang

Open Source Erlang is the standard implementation of Erlang. You can use Open Source Erlang to build commercial products without having to pay royalties or licence fees to Ericsson. Open Source Erlang uses the Apache License 2.0.

8.2  What Experimental, Research and Historical Implementations are there?

• High Performance Erlang (HiPE) is part of ordinary Open Source Erlang. It allows compiling Erlang modules to native code.

• Erjang is an experimental Erlang VM implemented in Java.

• Erlang to Scheme Compiler (ETOS). ETOS was another research project to compile Erlang programs to native code by first translating the program into scheme. They have some impressive benchmarks. ETOS is no longer under active development.

• Geoff's Erlang (GERL) supported a subset of the Erlang language. GERL compiled to native code via C. GERL has fallen into disuse.

• Safe Erlang was a prototype made by extending an older version of Ericsson's implementation. It was intended for applications where Erlang nodes must cooperate with other Erlang nodes which are not trusted. Safe Erlang is no longer under active development.

8.3  Which version of Erlang am I running?

The easiest way to tell is to look at the banner Erlang prints at startup, e.g.

        Erlang/OTP 17 [RELEASE CANDIDATE 1] [erts-6.0] [source] [64-bit] [smp:2:2] [async-threads:10] [hipe] [kernel-poll:false]
	

From Erlang code, in recent releases, call erlang:system_info(otp_release) to find out which release you are running.

8.4  What operating systems does Erlang run on?

Erlang runs on most unix and unix-like systems and on the currently popular flavours of windows. Ericsson have compiled it for

• BSD

• Linux

• Microsoft Windows

• OSX

• Solaris

• TRU64

• VxWorks

There are reports on the mailing list of other people compiling it successfully on IRIX, along with reports of Erlang running on less usual systems such as iPhones, Xboxes, QNX, Tilera 64-core CPUs and many embedded systems.

8.5  What implementations of the Erlang Virtual Machine are there?

Almost everyone uses "the new BEAM", where BEAM stands for Bogdan/Björn's Erlang Abstract Machine. This is the virtual machine supported in the commercial release.

The other virtual machines are of mostly historical interest:

JAM

This was the original Erlang virtual machine, inspired by the (Prolog) WAM. JAM stands for "Joe's Abstract Machine".

old BEAM

This was an attempt to compile Erlang to C, and then compile the C to native code. It was abandoned after benchmarking showed that the resulting code was only faster than VM-based Erlang for small programs.

8.6  Can Erlang be compiled under Microsoft Windows?

HOWTO/INSTALL-WIN32.md in the source code distribution which explains how to do this.

8.7  How can I cross-compile Erlang?

The standard Erlang/OTP distribution includes support and documentation for cross compiling. This is described in the HOWTO/INSTALL-CROSS.md file in the Erlang source, available from the downloads page.

8.8  Is Erlang small enough for embedded systems?

Many people run Erlang on many different types of embedded systems such as mobile telephones, telecommunication switching equipment and in-car electronics.

Rule of thumb: if the embedded system can run an operating system like linux, then it is possible to get current implementations of Erlang running on it with a moderate amount of effort.

Getting Erlang to run on, say, an 8 bit CPU with 32kByte of RAM is not feasible.

People successfully run the Ericsson implementation of Erlang on systems with as little as 16MByte of RAM. It is reasonably straightforward to fit Erlang itself into 2MByte of persistent storage (e.g. a flash disk).

A 2MByte stripped Erlang system can include the beam emulator and almost all of the stdlib, sasl, kernel, inets and runtime_tools libraries, provided the libraries are compiled without debugging information and are compressed.