SM is a Java-like DSL for modeling simple state machines. It supports a subset of the standard object-oriented approach, namely namespaces (here: packages), classes (here: machines), fields and methods.
In addition, you can also natively define states an instance can be in, events a machine can receive and transitions which should be performed when an event is processed. To make this work, the action language provides a statement for raising an event in an instance and an expression for checking the current state of a machine.
SM is made with Xtext & Xtend, and is based on Xbase, the reusable expression language of Xtext. As a result, integration with Java and the Eclipse IDE can be realized with little effort. This project serves as a teaching material for a master's course on compilers at Eötvös Loránd University, Budapest, Hungary.
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Before starting, make sure you have a JDK 8 implementation installed on your computer. As this is not the latest version, on some GNU/Linux distributions you might need to use external package repositories to obtain it.
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SM is written for Eclipse, in Eclipse, therefore the next step is to acquire the host IDE. We recommend the Eclipse IDE for Java and DSL Developers package of Eclipse 2018-12. Slightly different versions might also work, but a matching Xtext SDK is mandatory.
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In Eclipse, import projects hu.elte.sm, hu.elte.sm.ide and hu.elte.sm.ui through File > Import... > General > Existing Projects into Workspace. Then launch the Generate SM (sm) Language Infrastructure configuration from Run > Run Configurations... > Mwe2 Launch and let the framework download ANTLR when asked about it.
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Once the language infrastructure is generated, after a healthy dose of cleans & rebuilds you should get no compiler errors. To actually try SM, fire up a runtime Eclipse instance through Run > Run Configurations... > Eclipse Application > Launch Runtime Eclipse and proceed to the next section of this guide.
The most convenient way of getting to know SM leads through the examples provided in project hu.elte.sm.examples. Import this into the previously started runtime Eclipse instance by selecting it in File > Import... > General > Existing Projects into Workspace.
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The Count example in package hu.elte.sm.examples.count contains a simple machine which can register and count ticks, where the latter depends on its current state. Notice how it is used as a conventional Java class inside Count.java, even with regards to generated members like the
handleEventmethod and theEventenum. -
Hospital presents a little more complicated example with three interacting machines simulating a doctor and two patients, randomly befriending and cross-infecting each other in the hope of eventual recovery. Several forms of both internal & external communication and state checks can be seen in action here, as well as the usage of Java-types inside SM.
You can also define your own SM projects by creating a standard Java project in File > New > Other... > Java > Java Project and then adding a plain file through File > New > Other... > General > File to it with extension sm (for example, Counter.sm). At this point, Eclipse will ask you whether you want to convert this project into an Xtext one, which offer you should gracefully accept. We also recommend attaching the Xtend Library to your SM projects by selecting Build Path > Add Libraries... from the project's context menu.
Finally, we advise trying out how the language infrastructure behaves under common Eclipse functions. Check the syntax highlighting, jump through references, look at the outline, produce validation errors, try your luck with quickfixes, ask the content assist, place breakpoints and start cross-language debugging.
This software is licensed under the MIT license. See file LICENSE for details.