What is Erlang written in?

Question

What is Ericsson's implementation of Erlang and Erlang/OTP written and compiled in? Is is assembly, C or Erlang itself?

Update 1: Thanks to DrJokepu. If I understand correctly, Erlang source-to-VM compiler is written in Erlang itself. But the VM is written in C.

Update 2: Hynek-Pichi-Vychodil pointed out a lot of details.

• VM and HW interacting drivers: in C.
• Compiler (to VM) and libraries: in Erlang.
• Extensions: Possible in any language by writing a port or an Erlang node in that language.

Answer 1

Erlang itself is written in Erlang. Sounds strange? Yes, because it is only partially true. OK look at it in more detail:

1. Erlang preprocessor is written in Erlang.
2. Erlang parser is written in Erlang.
3. Erlang compiler to BEAM (byte-code VM) is written in Erlang.
4. Erlang compiler to HiPE (native VM extension) is written in Erlang.
5. Erlang VM BEAM and HiPE is written mostly in C.
6. Linked-in drivers are written mostly in C. (They are plugged to VM and serves communication with outside world.)
7. OTP is written in Erlang.
8. Another ports or nodes can be written in any language.

Answer 2

• 65.9% of erlang code is written in Erlang.
• 13.4% of erlang is written in XML.
• 13.6% of erlang is written in C.
• 1.4% of erlang is written in C++
• ...

You can see a live and update statistics in ohloh site, this report generate from main erlang git repository.

Answer 3

From the Erlang FAQ:

10.7 How did the first Erlang compiler get written?

(or: how was Erlang bootstrapped?) In Joe's words:

First I designed an abstract machine to execute Erlang. This was called the JAM machine; JAM = Joe's Abstract Machine.

Then I wrote a compiler from Erlang to JAM and an emulator to see if the machine worked. Both these were written in prolog.

At the same time Mike Williams wrote a C emulator for the JAM.

Then I rewrote the erlang-to-jam compiler in Erlang and used the prolog compiler to compile it. The resultant object code was run in the C emulator. Then we threw away prolog.