Port of the C# Stateless library to C++11. It's a lightweight state machine implementation with a fluent configuration interface.

The goal of the project is to provide an API that is as close as possible to that of the original C# library using only standard C++11 features. No external dependencies are required.

A simple example:

#include <stateless++/state_machine.hpp>
...
std::string on("On"), off("Off");
const char space(' ');

// Create a state machine with state type string and trigger type char.
// The state and trigger types can be any type that is
// - default constructible
// - assignable and copyable
// - equality comparable
// - less than comparable
state_machine<std::string, char> on_off_switch(off);

// Set up using fluent configuration interface.
on_off_switch.configure(off).permit(space, on);
on_off_switch.configure(on).permit(space, off);

// Drive the machine by firing triggers.
on_off_switch.fire(space); // <-- state is now "On"
...

See the bug tracker example for a more comprehensive use of the configuration API including parameterized triggers, sub-states and entry and exit actions.

The library is licensed under the terms of the Apache License 2.0.

Thanks to Nicholas Blumhardt for writing the original library in C# and making it available under a permissive license.

CMake build files are supplied to provide portability with minimal effort.

The library, example code and tests have been built and run on the following platforms:

• gcc 4.7.2 on Cygwin, gcc 4.7.3 on Ubuntu 12.04

  No known issues.

• Clang 3.1 on Cygwin

  Use the patch attached to this bug report to allow use of --std=gnu++11.

• Clang 3.2 on Ubuntu 12.04

  No known issues.

• Clang Apple LLVM version 4.2 on OS X, Darwin 12.4.0

  No known issues.

• Visual Studio 2012 on Windows 7

  Requires the Microsoft Visual C++ Compiler Nov 2012 CTP Toolset. The cmake build script attempts to configure this toolset but the cmake CMAKE_VS_PLATFORM_TOOLSET variable is currently read-only so you have to manually update the toolset in each project file to "Microsoft Visual C++ Compiler Nov 2012 CTP (v120_CTP_Nov2012)". This PowerShell script automates the process. If you want to run the script you may need to run PowerShell as Administrator and run Set-ExecutionPolicy Unrestricted first.

The library itself is header file only. The examples are built by default but this can be skipped if you just want to install the library header files. The unit tests use GoogleTest version 1.6.0. The project includes the fused gtest code so no additional dependencies need to be installed.

The instructions for UNIX-like platforms are:

git clone https://github.com/mattmason/cpp-stateless
mkdir build && cd build # Build without polluting the source tree
cmake -DCMAKE_INSTALL_PREFIX:PATH=/usr/local/ ../cpp-stateless

To build examples, build and run unit tests, and install the headers:

make && make test && make install # sudo may be required for make install

To install the headers without building examples and tests:

cd stateless++ && make install # sudo may be required for make install

For Visual Studio 2012 use the generated project files to build from within the IDE or on the command line.

Please feel free to contribute to the project. It's configured to build on drone.io after each commit so be prepared to receive emails to inform you of the outcome of your commit. Please don't exclude yourself from email notifications!

The state machine is currently quite rudimentary when compared to, for example, boost statechart. However, it's not intended to provide all the features of UML, or other, state machine specifications. Nevertheless, if you'd like to see a feature included, then please, go ahead and implement it. I'm happy to get involved too. In the first instance, create an issue or wiki page to share your idea.

One feature that would be useful is states with history. I haven't given it much thought yet, but it shouldn't be too hard to implement.

• Dynamic destination state selection.