antlr4-Can't load Hello as lexer or parser

antlr4
user3162707 picture user3162707 · Apr 26, 2014 · Viewed 23.3k times · Source

I recently have to use parser to do a project. I download ANTLR4 and follow the steps described in the book The Definitive ANTLR4 Reference. The following are the steps I type in command line:

 1. export CLASSPATH=".:/<Mydirectory>/antlr-4.2.2-complete.jar:$CLASSPATH"
 2. alias antlr4='java -jar /<My directory>/antlr-4.2.2-complete.jar'
 3. alias grun='java org.antlr.v4.runtime.misc.TestRig'
 4. antlr4 Hello.g4

All the things work fine, it generates java files that I need. However, after I enter 

 5. grun Hello r -tokens

It reports

Can't load Hello as lexer or parser.

I google some info, but still cannot figure out what happened.

Answer

Sam Harwell picture Sam Harwell · Apr 26, 2014

You generated Java source files by running ANTLR on the grammar, but TestRig is looking for compiled .class files. You need to run the Java compiler on the source files before using TestRig.

Related questions

ANTLR: Is there a simple example?

I'd like to get started with ANTLR, but after spending a few hours reviewing the examples at the antlr.org site, I still can't get a clear understanding of the grammar to Java process. Is there some simple example, something …

Read More
Handling errors in ANTLR4

The default behavior when the parser doesn't know what to do is to print messages to the terminal like: line 1:23 missing DECIMAL at '}' This is a good message, but in the wrong place. I'd rather receive this as …

Read More
How to create AST with ANTLR4?

I've been searching A LOT about this and I couldn't find anything useful that REALLY helps me build an AST. I already know that ANTLR4 doesn't build AST like ANTLR3 used to do. Everyone say: "Hey, use visitors!", but I …

Read More