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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 <https://web.archive.org/web/20180621053227/http://www.cse.unsw.edu.au/~chak/haskell/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
-----------------
Haddock is distributed with GHC distributions, and will automatically be provided if you use
`ghcup <https://www.haskell.org/ghcup>`__, for instance.
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 (c) 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:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. 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 AND CONTRIBUTORS
"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
OWNER OR CONTRIBUTORS 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
------------
A list of contributors to the project can be seen at
``https://github.com/haskell/haddock/graphs/contributors``.
Acknowledgements
----------------
Several documentation systems provided the inspiration for Haddock, most
notably:
- `IDoc <https://web.archive.org/web/20180621053227/http://www.cse.unsw.edu.au/~chak/haskell/idoc/>`__
- `HDoc <https://mail.haskell.org/pipermail/haskelldoc/2001-April/000067.html>`__
- `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.
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