• ANTLR
  • Setup

ANTLR

Search queries are built by an ANTLR language defined in pythia.g4 grammar. VSCode has a nice extension for ANTLR syntax support: ANTLR4 grammar syntax support.

You can also test online by pasting the Pythia g4 grammar into Parser and clearing Lexer in the ANTLR Online Lab.

Useful links:

• https://github.com/antlr/antlr4/tree/master/runtime/CSharp
• https://github.com/tunnelvisionlabs/antlr4cs
• https://www.antlr3.org/works/ for AntlrWorks GUI
• https://tomassetti.me/getting-started-with-antlr-in-csharp/
• https://levlaz.org/setting-up-antlr4-on-windows/

Setup

Setup in Windows is a bit more involved:

1. install Java runtime environment (v8 or higher).

2. download the ANTLR complete JAR from the ANTLR org website (https://www.antlr.org/download.html). The ANTLR tool converts grammars into programs that recognize sentences in the language described by the grammar. Place the JAR into some folder, e.g. C:\Javalib (or whatever else you like).

3. add the antlr-...complete.jar to CLASSPATH, either permanently (environment variables: create or append to CLASSPATH variable = .;C:\Javalib\antlr-4.9.2-complete.jar; note the trailing dot) or temporarily, at command line: SET CLASSPATH=.;C:\Javalib\antlr-4.10.1-complete.jar;%CLASSPATH%.

4. you can use these batches:

• compile: antlr.bat:

java org.antlr.v4.Tool %*

• test: grun.bat:

java org.antlr.v4.gui.TestRig %*

This batch starts from the grammar (.g4) file to build Java classes and compile, build C# classes, and run test on some expression stored in a file:

call C:\Javalib\antlr pythia.g4 -visitor
call C:\Javalib\antlr pythia.g4 -visitor -Dlanguage=CSharp -o .\cs\
javac *.java
call C:\Javalib\grun pythia query -gui .\grunsample.txt

To interactively invoke a test, run grun.bat (e.g. .\grun.bat pythia query -gui), then type and close the input stream by pressing CTRL+Z.