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Rosella Library

Rosella is a library of patterns and practices for use with the Parrot Virtual Machine. The Rosella project is actually a collection of several individual libraries, each of which implements a single pattern, best practice or toolset. Rosella is intended to be used piece-wise. Use only the parts you want and ignore the parts you do not want. Rosella libraries tend not to be interdependent, although some of the more advanced libraries rely on some of the more basic ones.

Project Goals

The Rosella project has a number of driving goals which influence both the types of libraries which are provided and the way those libraries are implemented:

  • Portability. Rosella is pure-parrot, and has no components written in C. It has no runtime dependencies besides a minimally-configured Parrot. Rosella can go anywhere Parrot can go.
  • Complete language agnosticism. Rosella intends to be usable from programs written in any language running on Parrot.
  • Encapsulate low-level details. Parrot provides lots of tools, though many are too low-level. Rosella attempts to encapsulate some ugly details behind nice, friendly, and usable interfaces.
  • Extensibility. Rosella aims to provide good defaults, but also to allow aggressive modifications, configurations, and subclassing behaviors to those who need something different.
  • Provide well-known tools. Rosella isn't an experimental research project. It aims to provide Parrot implementations of well-known patterns, practices, architectures, and tools. Rosella borrows good ideas from well-known and high-quality sources.
  • Focus on the user. Rosella is interested in making things easier for other coders. It wants to provide things that other coders will actually use and appreciate. Rosella is a set of tools for coders, not for end users.
  • Future Proof. Rosella provides interfaces, sometimes for very simple features or algorithms. In the future when Parrot changes or adds new features, Rosella will insulate the user from them. When Parrot adds proper threading, Rosella will be updated to provide thread-safety where needed.

Rosella Components

Rosella Stable Libraries

Here is a list of Rosella's libraries which are currently considered to be "stable" enough for general use:


Rosella's Core library provides a handful of routines used by the other Rosella libraries. This library provides basic behavior for working with an assortment of "type" meta-objects, and for implementing a standard system of object constructor behavior.


The Action library implements the Command pattern. Sequences of instructions can be bundled together into an Action object, and can be invoked later.


The Container library implements a Dependency Injection, Inversion of Control container type which can be used to help decouple modules in a program. The Container utilizes the Action library to setup constructor injection and method injection behaviors on registered types.


The Event library provides a subscribe/publish system to aide in aggressive application decoupling. Event publishers can be unaware of the details of event subscribers, and vice-versa. Applications become easier to maintain because important communication pathways do not need to have hard-coded senders and receivers.


The FileSystem library provides a friendly interface for working with the filesystem. It provides object types for files and directories and a number of utilities for working with each.


A companion to the Test library, The TAP Harness library implements the logic necessary to quickly construct a TAP harness for executing unit tests and reporting the results. Rosella's own test harness is written using this library.


The Memoize library adds in functionality to add memoization and caching to subroutines. There is a simple version and a version which uses proxies to add more features, but is slower.

Mock Object

The MockObject library uses the Rosella Proxy library to implement full-featured mock objects for use in testing with the Test library. Several tests in the Rosella test suite are implemented using this library.


The Path library provides utilities for searching the contents of large nested aggregate objects using string names.


The Proxy library provides the tools necessary to create a wide array of proxy objects.


The Query library provides a number of utilities for working with aggregate objects including higher-order functions, group operations, and data streams.


The String library provides a number of utilities and powerful interfaces for working with strings.


Inspired by testing libraries such as xUnit and Test::More, The Rosella Test library provides the tools and utilities to quickly write unit tests for your software. Rosella's own test suite is written using this library.


The Template library provides an engine for text templating tasks.


The Winxed library contains a number of tools for building Winxed-based projects.

Rosella Development Libraries

Rosella has a number of other libraries in planning and development. These libraries are not yet considered mature enough to include as part of a regular release. For the complete list with descriptions and ideas, see the future libraries page.


Build Dependencies

  • Parrot : Rosella runs on top of the Parrot VM. You cannot build, run, or use Rosella in any way without Parrot.
  • Winxed : Rosella is written in the Winxed language. You need Winxed to build Rosella, but you do not need Winxed to run it. Winxed has no runtime libraries of its own.

Installing With Plumage

Plumage is a package-management program for Parrot. If you have Plumage and Winxed already installed getting Rosella is a breeze:

$ plumage install rosella

That's all there is to it! You now have Rosella. If you don't have Plumage on your system you'll need to follow the rest of the instructions below.

Get the Source

You can download this project in either zip or tar formats.

You can also clone the project with Git by running:

$ git clone git://

Installing Manually

Once you have a copy of the source and all the necessary dependencies you can build, test and install Rosella:

$ winxed setup.winxed build
$ winxed setup.winxed test
$ winxed setup.wixned install

Project Info


Rosella is released under the terms of the Artistic 2.0 license. See the LICENSE file in the repo for more details.


Rosella is written by Whiteknight ( See the CREDITS file in the repo for more details about contributors and the people and projects which have inspired Rosella.

get the source code on GitHub : Whiteknight/Rosella
The image of the Crimson Rosella at the top of the page is from D. Gordon E. Robertson on Wikipedia . The image is released under the terms of the CC-By-SA-3.0 and/or the GFDL licenses.
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