Erlang is a functional programming language without so much as a single iteration construct; if you want a loop, you have to use recursion. Variables are immutable, and it communicates via asynchronous messages between lightweight processes.
Erlang is a functional programming language without so much as a single iteration construct; if you want a loop, you have to use recursion.
To keep it from sounding too terrible, Erlang has all the standard map/foreach/fold functions that every other functional language has; it's all recursion at the bottom, but it's nicely encapsulated. Most data structures follow the conventions of the iteration functions found in the lists module: http://erlang.org/doc/man/lists.html
Variables are immutable, and it communicates via asynchronous messages between lightweight processes.
I don't know if couch, riak, or rabbit use them, but erlang does have the process dictionary, which is a per-"thread" mutable datastore (http://www.erlang.org/course/advanced.html#dict). I know that wings3d uses the process dictionary a lot, supposedly for performance reasons. The use of the process dictionary isn't recomended, but it is there when needed.
EDIT: corrected an instance of rabbit where I meant erlang