Introduction
============

This is Haddock, a tool for automatically generating documentation from
annotated Haskell source code. Haddock was designed with several goals
in mind:

-  When documenting APIs, it is desirable to keep the documentation
   close to the actual interface or implementation of the API,
   preferably in the same file, to reduce the risk that the two become
   out of sync. Haddock therefore lets you write the documentation for
   an entity (function, type, or class) next to the definition of the
   entity in the source code.

-  There is a tremendous amount of useful API documentation that can be
   extracted from just the bare source code, including types of exported
   functions, definitions of data types and classes, and so on. Haddock
   can therefore generate documentation from a set of straight Haskell
   98 modules, and the documentation will contain precisely the
   interface that is available to a programmer using those modules.

-  Documentation annotations in the source code should be easy on the
   eye when editing the source code itself, so as not to obscure the
   code and to make reading and writing documentation annotations easy.
   The easier it is to write documentation, the more likely the
   programmer is to do it. Haddock therefore uses lightweight markup in
   its annotations, taking several ideas from
   `IDoc <http://freshmeat.sourceforge.net/projects/idoc/>`__. In fact,
   Haddock can understand IDoc-annotated source code.

-  The documentation should not expose any of the structure of the
   implementation, or to put it another way, the implementer of the API
   should be free to structure the implementation however he or she
   wishes, without exposing any of that structure to the consumer. In
   practical terms, this means that while an API may internally consist
   of several Haskell modules, we often only want to expose a single
   module to the user of the interface, where this single module just
   re-exports the relevant parts of the implementation modules.

   Haddock therefore understands the Haskell module system and can
   generate documentation which hides not only non-exported entities
   from the interface, but also the internal module structure of the
   interface. A documentation annotation can still be placed next to the
   implementation, and it will be propagated to the external module in
   the generated documentation.

-  Being able to move around the documentation by following hyperlinks
   is essential. Documentation generated by Haddock is therefore
   littered with hyperlinks: every type and class name is a link to the
   corresponding definition, and user-written documentation annotations
   can contain identifiers which are linked automatically when the
   documentation is generated.

-  We might want documentation in multiple formats - online and printed,
   for example. Haddock comes with HTML, LaTeX, and Hoogle backends, and
   it is structured in such a way that adding new backends is
   straightforward.

Obtaining Haddock
-----------------

Distributions (source & binary) of Haddock can be obtained from its `web
site <http://www.haskell.org/haddock/>`__.

Up-to-date sources can also be obtained from our public GitHub
repository. The Haddock sources are at
``https://github.com/haskell/haddock``.

License
-------

The following license covers this documentation, and the Haddock source
code, except where otherwise indicated.

    Copyright 2002-2010, Simon Marlow. All rights reserved.

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions
    are met:

    -  Redistributions of source code must retain the above copyright
       notice, this list of conditions and the following disclaimer.

    -  Redistributions in binary form must reproduce the above copyright
       notice, this list of conditions and the following disclaimer in
       the documentation and/or other materials provided with the
       distribution.

    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS "AS IS" AND ANY
    EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
    IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
    PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS BE
    LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
    CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
    SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
    BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
    LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
    NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
    SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Contributors
------------

Haddock was originally written by Simon Marlow. Since it is an open
source project, many people have contributed to its development over the
years. Below is a list of contributors in alphabetical order that we
hope is somewhat complete. If you think you are missing from this list,
please contact us.

-  Ashley Yakeley
-  Benjamin Franksen
-  Brett Letner
-  Clemens Fruhwirth
-  Conal Elliott
-  David Waern
-  Duncan Coutts
-  George Pollard
-  George Russel
-  Hal Daume
-  Ian Lynagh
-  Isaac Dupree
-  Joachim Breitner
-  Krasimir Angelov
-  Lennart Augustsson
-  Luke Plant
-  Malcolm Wallace
-  Manuel Chakravarty
-  Mark Lentczner
-  Mark Shields
-  Mateusz Kowalczyk
-  Mike Thomas
-  Neil Mitchell
-  Oliver Brown
-  Roman Cheplyaka
-  Ross Paterson
-  Sigbjorn Finne
-  Simon Hengel
-  Simon Marlow
-  Simon Peyton-Jones
-  Stefan O'Rear
-  Sven Panne
-  Thomas Schilling
-  Wolfgang Jeltsch
-  Yitzchak Gale

Acknowledgements
----------------

Several documentation systems provided the inspiration for Haddock, most
notably:

-  `IDoc <http://freshmeat.sourceforge.net/projects/idoc/>`__

-  `HDoc <https://web.archive.org/web/20010603070527/http://www.fmi.uni-passau.de/~groessli/hdoc/>`__

-  `Doxygen <https://www.doxygen.nl/index.html>`__

and probably several others I've forgotten.

Thanks to the the members of haskelldoc@haskell.org,
haddock@projects.haskell.org and everyone who contributed to the many
libraries that Haddock makes use of.
