Description:

Haddock is a tool for automatically generating documentation from
annotated Haskell source code. It is primary intended for documenting
libraries, but it should be useful for any kind of Haskell code.

Haddock lets you write documentation annotations next to the
definitions of functions and types in the source code, in a syntax
that is easy on the eye when writing the source code (no heavyweight
mark-up). The documentation generated by Haddock is fully hyperlinked
-- click on a type name in a type signature to go straight to the
definition, and documentation, for that type.

Haddock can generate documentation in multiple formats; currently HTML
is implemented, and there is partial support for generating DocBook.
The generated HTML uses stylesheets, so you need a fairly up-to-date
browser to view it properly (Mozilla, Konqueror, Opera, and IE 6
should all be ok).