# datum : "scrap your boilerplate" for Erlang
> You could do this with a macro, but...
> the best macro is a macro you don't maintain
**datum** is a pure functional and generic programming for Erlang. It had its origins in [Purely Functional Data Structures](https://www.cs.cmu.edu/~rwh/theses/okasaki.pdf) by Chris Okasaki, on implementing a various higher rank functional abstractions and patterns, on dealing with [scrap your boilerplate](https://www.microsoft.com/en-us/research/publication/scrap-your-boilerplate-with-class/) and gaining experience from other functional languages primary Scala and Haskell. The library is still testing the limits of functional abstractions in Erlang.
## Key features
The [feature overview](doc/features.md) provides an introduction to datum features, use-cases and reasoning of they existence:
* data structures with common behavior: **foldable**, **traversable** and **map-like** including
* pure functional **data types**: binary search tree, red-black tree, heap, queues, streams and others
* resembles concept of getters and setters ([**lens**](doc/lens.md)) for complex algebraic data types.
* define a **category pattern** and **monads**
* [type casts](doc/typecast.md) of scalar (primitive) data types
* supports **OTP/18.x** or later release
**Cheat Sheet** is available [here](doc/cheatsheet.md)
## Getting started
The latest version of the library is available at its `master` branch. All development, including new features and bug fixes, take place on the `master` branch using forking and pull requests as described in contribution guidelines.
The stable library release is available via hex packages, add the library as dependency to `rebar.config`
## How To Contribute
The library is Apache 2.0 licensed and accepts contributions via GitHub pull requests:
* Fork the repository on GitHub
* Read build instructions
* Make a pull request
The build process requires [Erlang/OTP](http://www.erlang.org/downloads) version 19.0 or later and essential build tools.
**Build** and **run** service in your development console. The following command boots Erlang virtual machine and opens Erlang shell.
git clone https://github.com/fogfish/datum
### commit message
The commit message helps us to write a good release note, speed-up review process. The message should address two question what changed and why. The project follows the template defined by chapter [Contributing to a Project](http://git-scm.com/book/ch5-2.html) of Git book.
> Short (50 chars or less) summary of changes
> More detailed explanatory text, if necessary. Wrap it to about 72 characters or so. In some contexts, the first line is treated as the subject of an email and the rest of the text as the body. The blank line separating the summary from the body is critical (unless you omit the body entirely); tools like rebase can get confused if you run the two together.
> Further paragraphs come after blank lines.
> Bullet points are okay, too
> Typically a hyphen or asterisk is used for the bullet, preceded by a single space, with blank lines in between, but conventions vary here
If you experience any issues with the library, please let us know via [GitHub issues](https://github.com/fogfish/datum/issue). We appreciate detailed and accurate reports that help us to identity and replicate the issue.
* **Specify** the configuration of your environment. Include which operating system you use and the versions of runtime environments.
* **Attach** logs, screenshots and exceptions, in possible.
* **Reveal** the steps you took to reproduce the problem, include code snippet or links to your project.
Copyright 2012 Dmitry Kolesnikov
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0.
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.