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

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
simonpeter
When I try the command to create a pair of migration files I get an error. user=&gt; (create-migration "guestbook") Execution error (Ill...
New
jdufour
Hello! On page xix of the preface, it says there is a community forum "… for help if your’re stuck on one of the exercises in this book… ...
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
Chrichton
Dear Sophie. I tried to do the “Authorization” exercise and have two questions: When trying to plug in an email-service, I found the ...
New
Charles
In general, the book isn’t yet updated for Phoenix version 1.6. On page 18 of the book, the authors indicate that an auto generated of ro...
New
creminology
Skimming ahead, much of the following is explained in Chapter 3, but new readers (like me!) will hit a roadblock in Chapter 2 with their ...
New
rainforest
Hi, I’ve got a question about the implementation of PubSub when using a Phoenix.Socket.Transport behaviour rather than channels. Before ...
New
jwandekoken
Book: Programming Phoenix LiveView, page 142 (157/378), file lib/pento_web/live/product_live/form_component.ex, in the function below: d...
New
andreheijstek
After running /bin/setup, the first error was: The foreman' command exists in these Ruby versions: That was easy to fix: gem install fore...
New

Other popular topics Top

PragmaticBookshelf
Brace yourself for a fun challenge: build a photorealistic 3D renderer from scratch! In just a couple of weeks, build a ray tracer that r...
New
PragmaticBookshelf
Free and open source software is the default choice for the technologies that run our world, and it’s built and maintained by people like...
New
New
AstonJ
Saw this on TikTok of all places! :lol: Anyone heard of them before? Lite:
New
AstonJ
If you want a quick and easy way to block any website on your Mac using Little Snitch simply… File &gt; New Rule: And select Deny, O...
New
PragmaticBookshelf
Author Spotlight: VM Brasseur @vmbrasseur We have a treat for you today! We turn the spotlight onto Open Source as we sit down with V...
New
sir.laksmana_wenk
I’m able to do the “artistic” part of game-development; character designing/modeling, music, environment modeling, etc. However, I don’t...
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
Margaret
Ask Me Anything with Mark Volkmann @mvolkmann On February 24 and 25, we are giving you a chance to ask questions of PragProg author M...
New

Sub Categories: