Haml is a templating engine for HTML. It's designed to make it both easier and more pleasant to write HTML documents, by eliminating redundancy, reflecting the underlying structure that the document represents, and providing an elegant syntax that's both powerful and easy to understand.

Haml can be used from the command line or as part of a Ruby web framework. The first step is to install the gem:

gem install haml

After you write some Haml, you can run

haml document.haml

to compile it to HTML. For more information on these commands, check out

haml --help

To use Haml programatically, check out the YARD documentation.

To use Haml with Rails, simply add Haml to your Gemfile and run bundle.

If you'd like to replace Rails's Erb-based generators with Haml, add haml-rails to your Gemfile as well.

The most basic element of Haml is a shorthand for creating HTML:

%tagname{:attr1 => 'value1', :attr2 => 'value2'} Contents

No end-tag is needed; Haml handles that automatically. If you prefer HTML-style attributes, you can also use:

%tagname(attr1='value1' attr2='value2') Contents

Adding class and id attributes is even easier. Haml uses the same syntax as the CSS that styles the document:

%tagname#id.class

In fact, when you're using the <div> tag, it becomes even easier. Because <div> is such a common element, a tag without a name defaults to a div. So

#foo Hello!

becomes

<div id='foo'>Hello!</div>

Haml uses indentation to bring the individual elements to represent the HTML structure. A tag's children are indented beneath than the parent tag. Again, a closing tag is automatically added. For example:

%ul
  %li Salt
  %li Pepper

becomes:

<ul>
  <li>Salt</li>
  <li>Pepper</li>
</ul>

You can also put plain text as a child of an element:

%p
  Hello,
  World!

It's also possible to embed Ruby code into Haml documents. An equals sign, =, will output the result of the code. A hyphen, -, will run the code but not output the result. You can even use control statements like if and while:

%p
  Date/Time:
  - now = DateTime.now
  %strong= now
  - if now > DateTime.parse("December 31, 2006")
    = "Happy new " + "year!"

Haml provides far more tools than those presented here. Check out the reference documentation for full details.

Haml's indentation can be made up of one or more tabs or spaces. However, indentation must be consistent within a given document. Hard tabs and spaces can't be mixed, and the same number of tabs or spaces must be used throughout.

Contributions are welcomed, but before you get started please read the guidelines.

After forking and then cloning the repo locally, install Bundler and then use it to install the development gem dependecies:

gem install bundler
bundle install

Once this is complete, you should be able to run the test suite:

rake

You'll get a warning that you need to install haml-spec, so run this:

git submodule update --init

At this point rake should run without error or warning and you are ready to start working on your patch!

Note that you can also run just one test out of the test suite if you're working on a specific area:

ruby -Itest test/helper_test.rb -n test_buffer_access

Haml was created by Hampton Catlin, the author of the original implementation. However, Hampton doesn't even know his way around the code anymore and now just occasionally consults on the language issues.

Nathan Weizenbaum was for many years the primary developer and architect of the "modern" Ruby implementation of Haml. His hard work endlessly answering forum posts, fixing bugs, refactoring, finding speed improvements, writing documentation, and implementing new features is what has kept the project alive.

Norman Clarke, the author of Haml Spec and the Haml implementation in Lua, took over as maintainer in April 2012.

Some of Nathan's work on Haml was supported by Unspace Interactive.

Beyond that, the implementation is licensed under the MIT License.

Copyright (c) 2006-2009 Hampton Catlin and Nathan Weizenbaum

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.