dtonhofer

dtonhofer

The Definitive ANTLR 4 Reference - "Java.g4" grammer (used on page 40) no longer passes ANTLR

@parrt

In the context of Chapter 4.3, the grammar Java.g4, meant to parse Java 6 compilation units, no longer passes ANTLR (currently 4.10.1)

That file is included in the Zip file of examples & source code that comes with the book (as code/tour/Java.g4)

Two problems:

The definition of “expression” uses “<assoc=right>” on each operator from line 546 onwards. However, “<assoc=right>” now needs to be placed in front:

    |   <assoc=right> expression
        ('^='
        |'+='
        |'-='
        |'*='
        |'/='
        |'&='
        |'|='
        |'='
        |'>' '>' '='
        |'>' '>' '>' '='
        |'<' '<' '='
        |'%='
        ) 

The definitin for “Escape Sequence” contains the string ‘"’ which is considered an illegal escape. The backslash has to be removed.

In fact, the current ANTLR distro comes with its own Java.g4, or rather two of them (very confusing!)

A grammer for Java 7 from 2013:

antlr4-4.10.1/runtime-testsuite/test/org/antlr/v4/test/runtime/java/api/Java.g4

A grammar for Java 5 from 2008;

antlr4-4.10.1/tool-testsuite/test/org/antlr/v4/test/tool/Java.g4

The example code should probably be upgrade to

antlr4-4.10.1/runtime-testsuite/test/org/antlr/v4/test/runtime/java/api/Java.g4

which seems to work.

Marked As Solved

ariel.lenis

ariel.lenis

Thank you @dtonhofer and @parrt I was able to make it work using the grammars from

https://github.com/antlr/grammars-v4/tree/master/java/java

You need to generate the Java files in order: Lexer first and Parser last

antlr4 JavaLexer.g4
antlr4 JavaParser.g4

And finally this is the code that I have used for the ExtractInterfaceListener.java file:

import org.antlr.v4.runtime.TokenStream;

public class ExtractInterfaceListener extends JavaParserBaseListener {
    JavaParser parser;
    public ExtractInterfaceListener(JavaParser parser) {this.parser = parser;}

    @Override
    public void enterClassDeclaration(JavaParser.ClassDeclarationContext ctx) {
        // Errata Suggestion: previous implementation
        // System.out.println("interface I" + ctx.Identifier() + " {");
        // Errata Suggestion: fix
        System.out.println("interface I" + ctx.identifier().getText() + " {");
    }

    @Override
    public void exitClassDeclaration(JavaParser.ClassDeclarationContext classDeclarationContext) {
        System.out.println("}");
    }

    @Override
    public void enterMethodDeclaration(JavaParser.MethodDeclarationContext ctx) {
        // need parser to get tokens
        TokenStream tokens = parser.getTokenStream();
        
        /*
        // Errata Suggestion: previous implementation
        String type = "void";

        if ( ctx.type()!=null ) {
            type = tokens.getText(ctx.type());
        }
        */
        // Errata Suggestion: fix
        String type = ctx.typeTypeOrVoid().getText();

        String args = tokens.getText(ctx.formalParameters());

        // Errata Suggestion: previous implementation
        // System.out.println("\t" + type + " " + ctx.Identifier() + args + ";");
        // Errata Suggestion: fix
        System.out.println("\t" + type + " " + ctx.identifier().getText() + args + ";");
    }
}

I hope it will help someone.

Where Next?

Popular Pragmatic Bookshelf topics Top

jamis
The following is cross-posted from the original Ray Tracer Challenge forum, from a post by garfieldnate. I’m cross-posting it so that the...
New
herminiotorres
Hi! I know not the intentions behind this narrative when called, on page XI: mount() |&gt; handle_event() |&gt; render() but the correc...
New
alanq
This isn’t directly about the book contents so maybe not the right forum…but in some of the code apps (e.g. turbo/06) it sends a TURBO_ST...
New
New
jgchristopher
“The ProductLive.Index template calls a helper function, live_component/3, that in turn calls on the modal component. ” Excerpt From: Br...
New
jskubick
I found an issue in Chapter 7 regarding android:backgroundTint vs app:backgroundTint. How to replicate: load chapter-7 from zipfile i...
New
Keton
When running the program in chapter 8, “Implementing Combat”, the printout Health before attack was never printed so I assumed something ...
New
ggerico
I got this error when executing the plot files on macOS Ventura 13.0.1 with Python 3.10.8 and matplotlib 3.6.1: programming_ML/code/03_...
New
gorkaio
root_layout: {PentoWeb.LayoutView, :root}, This results in the following following error: no “root” html template defined for PentoWeb...
New
davetron5000
Hello faithful readers! If you have tried to follow along in the book, you are asked to start up the dev environment via dx/build and ar...
New

Other popular topics Top

New
dasdom
No chair. I have a standing desk. This post was split into a dedicated thread from our thread about chairs :slight_smile:
New
AstonJ
poll poll Be sure to check out @Dusty’s article posted here: An Introduction to Alternative Keyboard Layouts It’s one of the best write-...
New
New
New
AstonJ
This looks like a stunning keycap set :orange_heart: A LEGENDARY KEYBOARD LIVES ON When you bought an Apple Macintosh computer in the e...
New
First poster: AstonJ
Jan | Rethink the Computer. Jan turns your computer into an AI machine by running LLMs locally on your computer. It’s a privacy-focus, l...
New
AstonJ
If you’re getting errors like this: psql: error: connection to server on socket “/tmp/.s.PGSQL.5432” failed: No such file or directory ...
New
AstonJ
Curious what kind of results others are getting, I think actually prefer the 7B model to the 32B model, not only is it faster but the qua...
New
PragmaticBookshelf
A concise guide to MySQL 9 database administration, covering fundamental concepts, techniques, and best practices. Neil Smyth MySQL...
New

Sub Categories: