Erlang programming language

It is named after A. K. Erlang. It is sometimes mistakenly thought that its name is as abbreviation of ERicsson LANGuage, owing to its heavy use inside Ericsson.

Functional language

Code looks like this:

-module(fact). -export([fac/1]). fac(0) -> 1; fac(N) where N > 0 -> N * fac(N-1). Below is an implementation of a Quicksort algorithm.

%% quicksort(List) %% Sort a list of items -module(quicksort). -export([qsort/1]). qsort([]) -> []; qsort([Pivot|Rest]) -> qsort([ X || X <- Rest, X < Pivot]) ++ [Pivot] ++ qsort([ Y || Y <- Rest, Y >= Pivot]). The above example recursively calls the function qsort until there is no more to be sorted. The expression [ X || X <- Rest, X < Pivot] can be read as "Chose all X where X is a member of Rest and X is less then Pivot", resulting in a very easy way of handling Lists. Since you can evaluate any boolean expression between two different datatypes, the evaluation is straight forward - for example, 1 < a will return true.

However, a compare function can be used if the order on which Erlang bases its return value (true or false) needs to be changed. For example, if we would want an ordered list where a > 1 evaluates true.

Concurrency oriented language

Code examples:
Pid = spawn(Mod, Func, Args) % execute function Func as new thread

Pid ! a_message % send message to the thread (asynchronously) receive % receive message sent to this thread a_message -> do_something end. Erlang contains mechanisms to deal with errors and to ensure high availability of the whole system. Dynamical replacement of code (hot swapping) is supported.

Distribution

Since taking the open source path in 1998, it became used by several companies world-wide, including Nortel and T-Mobile. However, it didn't and hasn't yet become a wide-spread mainstream programming language.

As of 2005, Erlang is under active development with regular releases. It is available for several Unix-like operating systems and Windows.

Advantages