A lightweight, image based, encapsulated development environment based around Smalltalk, specifically, "A Little Smalltalk" version 3.0 by Timothy A. Budd.

The reason for basing on the 3.0 version of the LST system, and not the more recent 4.x version, is that firstly, 3.0 is public domain, and secondly, the 3.0 codebase is much clearer and simpler to follow and understand. Tumbleweed began as a learning exercise, so having a clear and relatively simple codebase to start from was more important than the optmisations and other improvements that came about with the rewrite to version 4.

Work is underway to update and improve the system as a whole, focusing in the following areas.

• Add a foreign function interface using libffi. This allows direct access to shared library functionality without having to extend the VM.
• Extend the basic language functionality to include MetaClass support. The MetaClass support follows the standard Smalltalk approach, all classes have a unique MetaClass, automatically created when the Class is created. MetaClasses support class methods and data.
• Extend the basic language class hierarchy to support method categories.
• Replace the memory management with a simple mark/sweep garbage collection scheme.
• Various optimisations to the language interpreter to improve message throughput.

Tumbleweed currently has very little in the way of dependencies. Build is via CMake, you should build out of source. The following instructions are for Posix based systems, Windows is similar, the required changes should be obvious.

The CMake configuration exposes some options to control the build.

• TW_BUILD_TESTS

  Enable the Google Test based unit testing. You will need to make sure the GTEST_* options are also correctly setup.

• TW_ENABLE_FFI

  Enable the support for dynamically binding shared libraries via the libffi library. You'll need to make sure that LIBFFI_* options are also correctly setup.

• TW_SMALLINTEGER_AS_OBJECT

  By default Tumbleweed treats small integers as a special type for efficiency. This flag will switch to treating them as normal objects. There is a significant performance hit with this approach, it is only really to be used while the new approach is being finalised.

Get the source from github:

git clone git://github.com/pgregory/tumbleweed.git

Make a build directory, and configure with cmake:

mkdir build
cd build
cmake ../tumbleweed
make

You should then end up with an executable 'tw' in the build folder. To work with the GUI, you'll need a copy of the IUP shared library (.so or .dll) in the same foler. Tumbleweed will work fine without it, but you'll only be able to work from the command line.

Run Tumbleweed:

./tw

You can then run standard Smalltalk like commands from the command prompt.

> 'Hello, World!' print
'Hello, World!'
'Hello, World!'

The second 'Hello, World!' is because Tumbleweed by default echos the result of an expression.