Installing Factor

Installing Factor, and making Factor and Exercism play nice

Even if you already have Factor 0.98 installed, you still need to read the last section of this document for important information about testing Factor code in the Exercism environment.

Installing Factor

To install Factor, you need a nightly or bleeding-edge build.

The last stable release of Factor (0.97 released 2 Nov 2014) is too old for use with Exercism.

Nightly provides nightly binaries under the "Development release" section. These binaries are built from git, but only builds that pass are shown.

(Auto)build from source

If you want the bleeding edge and even nightly is too old for you, then you will need a modern C++ compiler (GCC >=4.8 or Clang >=3.5), make, and curl.

With those simple requirements fulfilled, you can:

  1. Download the build shell script: here for Unix-likes / POSIX shells or here for Windows. Put it in the directory under which Factor should be installed. A directory called factor containing the codebase will be created.

  2. Run it like ./ install, or .\build.cmd install on Windows. This will clone Factor's git repository, build it, and download a Factor VM image from This process may take between 2 and 20 minutes, scaling with your link and clock speeds.

  3. You can now run the factor or factor.exe binary generated inside the factor subdirectory. Try factor --help for help. You can also access documentation from the command line, or by pressing F1 in the GUI Listener, which will open the help browser.

  4. In the future, use the or (build.cmd on Windows) inside the factor subdirectory to pull from git and rebuild in-place, and download a new VM image if needed.

The file structure may now look like this:


You no longer need the top level build script, as in the future the downloaded one should be used.

Manually build from source (not recommended)

Clone the repository and use make in that folder.

If make fails with an error about a non-present target, try make factor or, if you can read a Makefile, find the make target for your platform in GNUmakefile.

If that fails, open an issue on factor/factor containing the error -- the friendly developers will be happy to help.

Stable (not recommended)

Note that Exercism and the exercism vocabulary for Factor exercises on Exercism both require at least a nightly build.

Only use a stable release if you plan to skip automated testing or thousands of new features and bugfixes, and you do not plan to contribute to Factor exercises on Exercism.

To develop Factor exercises for Exercism, you need to be able to build and run the exercism vocabulary.

Download a Stable release binary for your platform from the "Stable release" section on, and run the installer.

Making Exercism and Factor work together

Due to limitations like name clashes and filename disagreements, it's rather difficult to use Factor's tools.test on Exercism exercises out of the box.

Instead, there is a wrapper testing vocabulary for the Factor workflow in an Exercism context. Users and Exercism maintainers alike can write and run tests in a familiar way, with much less overhead.

To test your Factor solutions in your exercism/factor folder, follow the directions in the README.

For information on using the exercism.testing vocabulary, refer to the testing documentation, or to exercism.testing's documentation by running "exercism.testing" help in Factor, after installing exercism.testing.

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