83 lines
4.0 KiB
Markdown
83 lines
4.0 KiB
Markdown
Title: The Spoofax Propositional Language
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# Stratego Transformations in the Spoofax Eclipse IDE
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The Stratego Tutorial/Reference {! docrefs/manual.md !} in the official Spoofax
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documentation presents a comprehensive overview of the Stratego approach to
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abstract syntax tree (AST) transformations. It employs a running example of an
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abstract syntax intended to represent classical Propositional Logic, which we
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will dub here the "Spoofax Propositional Language." The manual introduces the
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concepts of rules and strategies for applying them, and then shows how both
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of those facilities can be created from more primitive operations of
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term matching and replacement. Every step of the way is illustrated with actual,
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working Stratego programs.
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This [Gitea repository](https://code.studioinfinity.org/glen/spoofax_prop)
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provides a working implementation of most of the examples in the manual.
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It can be cloned as an Eclipse project (note the git root
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is at the project level rather than in the directory above the project, as may
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be more common; in other words, this repository should be cloned within
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an existing Eclipse workspace, rather than as the workspace itself). Within that
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project, all of the examples from the Stratego Tutorial manual that employ the
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propositional language (see below), starting from Section 4 on, can be executed
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directly. This repository does not attempt to implement the portion of examples
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dealing with an arithmetical/imperative language (except in a couple of
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isolated instances in which the relevant phenomenon is recast in the
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propositional language).
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## Preliminaries
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I recommend working with a complete pre-built Eclipse installation of Spoofax
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as provided by the Spoofax project,
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for example one that you can download from their
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[development release page](https://www.metaborg.org/en/latest/source/release/development.html).
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Sometimes I have had difficulty getting the examples in this repository working
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starting from plain Eclipse and installing Spoofax in it using the Spoofax
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update site.
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If at any point in using the examples things appear to stop working, and
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especially if the Spoofax menu item disappears or the Spoofax menu turns into
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a thin white rectangle with no items to select, try the following:
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* Build the project and try again.
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* Clean the workspace, and when it is done, build the project again and try
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again.
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* Right click on the project, select Maven > Update Project, make sure
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everything is checked except "Offline" and
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"Force update of Snapshots/Releases", and then click "OK". When it is done,
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clean the workspace, then build the project and try again.
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* If that still hasn't done it, restart (the Spoofax version of!) Eclipse and
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clean the workspace, then build the project and try again.
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Running with a version of Spoofax _later_ than 2.5.13 (I was using a 2.6.0
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development snapshot), the Spoofax menu would always come back into proper
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operation at some point in the above process.
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## Abstract syntax
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With the preliminaries out of the way, note that the examples in the Stratego
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manual deal exclusively with Abstract Syntax Trees (ASTs). The trees used
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are primarily for a language concerning propositional logic, which we dub the
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Spoofax Propositional Language (SPL). It is defined
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at the top of {! docrefs/sec4.1.md !} of the manual.
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It consists of the following signature of constructors:
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```stratego
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{! src-gen/signatures/Spoofax-Propositional-Language-sig.str extract:
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start: '(signature[\s]*)$'
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stop: '^(\s*Eq\s*:.*)'
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!}
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```
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<!-- /md -->
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Continue reading in the latest released
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[SPL documentation](http://studioinfinity.org/SPL)
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to see how to define and run Stratego transformations on ASTs of this language.
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### Building the documentation
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In order to build the documentation from a clone of this repository, you must
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install [MkDocs](http://mkdocs.org) and the `semiliterate` plug-in for MkDocs,
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which is available in
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[pre-release form](https://code.studioinfinity.org/glen/mkdocs-semiliterate). Then
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you can execute `mkdocs build` in the top-level directory of this project.
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