Question

Is there any standard documentation (like UML for OO) for functional languages?
After downloading couch db which is written in erlang and looking at the source code I was shocked, there is hardly a line of documentation.
Is there no need to document how all these functions depend on each other?
Are there better documented medium size projects freely available too learn, how things are done using this paradigm?

Answer 1

The code should be documented, regardless of language.

There seems to be a standard documentation style called EDoc. EDoc is able to produce external API documentation; quoting from one source:

EDoc is the Erlang standard
application to document the Erlang API
directly inside the Erlang code.

This is referenced in the documentation section at erlang.org:

EDoc lets you write the documentation
of an Erlang program as comments in
the source code itself, using tags on
the form “@Name …”. A source file
does not have to contain tags for EDoc
to generate its documentation, but
without tags the result will only
contain the basic available
information that can be extracted from
the module.

A focused Google search will take you from here.