资源说明：Simple PL/0 Compiler that generates Java Bytecode, written in Ruby
PL/0 Compiler, written in Ruby
==============================
This is a simple *one-step* compiler, which generates valid **Java Bytecode**, written in Ruby.
More details can be found in the `relatorio-compilador.pdf` (pt-BR) document, but here is a summary:
- [RSpec](http://rspec.info) Specifications (Example Groups in `test` folder) are a good place to learn how the compiler should work.
- Sample PL/0 programs can be found in the `test/fixtures` directory.
- Automata (Finite State Machines) I'm using to parse code can be found in the `lib/machine` directory. They follow a domain specific language I've created in this project (`lib/state_machine.rb`) to describe automata.
- I am not using any parser generator, just because I wanted to deep learn how compilers work.
- The compiler generates Java Mnemonics, which are converted to Java Bytecode by the [Jasmin assembler](http://jasmin.sourceforge.net/).
- The PL/0 grammar I'm following can be seen in the `grammar.wirth` file. It is written in the [Wirth Syntax Notation](http://en.wikipedia.org/wiki/Wirth_syntax_notation).
Compiler Usage
==============
The `compile.rb` file acts as the compilation entry point; it starts the hole process. The `lib/` folder has the source code for all classes and the `test/` folder has unit tests, using [RSpec](http://rspec.info).
Minimum Requirements
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- [Java Runtime Environment](http://java.sun.com) (JRE) >= 1.5; the `java` command must be available in the `$PATH` environment variable.
Recommended Requirements
------------------------
- [Java Development Kit](http://java.sun.com) (JDK) >= 1.5;
- [Ruby interpreter](http://www.ruby-lang.org) >= 1.8.5;
- `java`, `ruby` and `rake` commands must be in the `$PATH`;
- [RubyGems](http://www.rubygems.org/) - `gem` command available in `$PATH`.
Running with the minimum requirements
-------------------------------------
[JRuby](http://jruby.codehaus.org), the Ruby interpreter written n Java, is embedded in the compiler for machines with only the Java Runtime Environment installed. In this case, Ruby code is executed by JVM.
- inside of the compiler folder, create a new PL/0 file. There are some examples available in the `test/fixtures` folder;
- to see the compiler usage instructions, run the `compile.bat` file inside some shell (cmd inside Windows, or sh inside unixes);
- still in the terminal window, to compile your PL/0 source:
compile
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