Book error?

[Mister Bean]

I've run into this problem running the first example in the book:

After creating the Hello.g4 sample grammar (see next)

grammar hello; // define a grammar called Hello
r : 'hello' ID; // match keyword 'hello' followed by an identifier
ID : [a-z]+; // match lower-case identifiers
WS : [ \t\r\n]+ -> skip ; //skip spaces, tables, newlines, \r (Windows) I generated and compiled the Java

I generated and compiled the Java code:

Hello.g4
Hello.tokens
HelloBaseListener.class
HelloBaseListener.java
HelloLexer.class
HelloLexer.java
HelloLexer.tokens
HelloListener.class
HelloListener.java
HelloParser$RContext.class
HelloParser.class
HelloParser.java

When I run grun from within the above directory, it gives an error message: "Can't load Hello as lexer or parser"

. . . . . . .

In addition, running grun with no parameters, does more than what the book says: It prints the usage messages *and* a NullPointerException stack trace:

TestRig.main ->
TestRig.process ->
java.lang.ClassLoader.loadClass ->
sun.misc.Launcher.$AppClassLoader.loadClass

I'm running on Windows 7 Ultimate x86, 4GB RAM, 8 cores.

What needs to be fixe? TIA

[Hilco Wijbenga]

This example works fine for me (on Linux, though). Are you sure your
grun.bat is correct? And surely there is more to the stack trace than
you included?

[Terence Parr]

Hi.  that is most likely a CLASSPATH issue. make sure the current directory is in the path.

Ter

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