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

jon
Some minor things in the paper edition that says “3 2020” on the title page verso, not mentioned in the book’s errata online: p. 186 But...
New
iPaul
page 37 ANTLRInputStream input = new ANTLRInputStream(is); as of ANTLR 4 .8 should be: CharStream stream = CharStreams.fromStream(i...
New
belgoros
Following the steps described in Chapter 6 of the book, I’m stuck with running the migration as described on page 84: bundle exec sequel...
New
raul
Hi Travis! Thank you for the cool book! :slight_smile: I made a list of issues and thought I could post them chapter by chapter. I’m rev...
New
jeremyhuiskamp
Title: Web Development with Clojure, Third Edition, vB17.0 (p9) The create table guestbook syntax suggested doesn’t seem to be accepted ...
New
leonW
I ran this command after installing the sample application: $ cards add do something --owner Brian And got a file not found error: Fil...
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
nicoatridge
Hi, I have just acquired Michael Fazio’s “Kotlin and Android Development” to learn about game programming for Android. I have a game in p...
New
brunogirin
When trying to run tox in parallel as explained on page 151, I got the following error: tox: error: argument -p/–parallel: expected one...
New
s2k
Hi all, currently I wonder how the Tailwind colours work (or don’t work). For example, in app/views/layouts/application.html.erb I have...
New

Other popular topics Top

Devtalk
Reading something? Working on something? Planning something? Changing jobs even!? If you’re up for sharing, please let us know what you’...
1052 21915 398
New
New
AstonJ
Just done a fresh install of macOS Big Sur and on installing Erlang I am getting: asdf install erlang 23.1.2 Configure failed. checking ...
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
AstonJ
In case anyone else is wondering why Ruby 3 doesn’t show when you do asdf list-all ruby :man_facepalming: do this first: asdf plugin-upd...
New
AstonJ
Continuing the discussion from Thinking about learning Crystal, let’s discuss - I was wondering which languages don’t GC - maybe we can c...
New
PragmaticBookshelf
Create efficient, elegant software tests in pytest, Python's most powerful testing framework. Brian Okken @brianokken Edited by Kat...
New
PragmaticBookshelf
Rails 7 completely redefines what it means to produce fantastic user experiences and provides a way to achieve all the benefits of single...
New
AstonJ
If you get Can't find emacs in your PATH when trying to install Doom Emacs on your Mac you… just… need to install Emacs first! :lol: bre...
New
PragmaticBookshelf
Get the comprehensive, insider information you need for Rails 8 with the new edition of this award-winning classic. Sam Ruby @rubys ...
New

Sub Categories: