On Sun, 3/1/09, Jeff Higgins wrote:
> Hi,
>
> I'm a beginner with JavaCC and am having
> problems understanding lexical states.
>
[snip]
The following solves the immediate problem,
but it seems not pretty somehow.
I hope to understand how to accomplish this
using a lexical state solution.
options {
JDK_VERSION = "1.5";
}
PARSER_BEGIN(EParser)
package scratch;
import java.io.*;
public class EParser {
public static void main(String args[])
throws ParseException {
Expression exp = null;
try {
EParser parser = new EParser(
new BufferedReader(new FileReader(args[0])));
exp = parser.expression();
if ( exp != null )
System.out.println( exp.toString() );
else
System.out.println( "exp == null" );
} catch(Exception e) {
e.printStackTrace();
}
}
}
PARSER_END(EParser)
SKIP : { " "|"\r"|"\t"|"\n" }
TOKEN :
{
< EXP:
"E"
(" "|"\r"|"\t"|"\n")*
"("
(~[])*
")"
(" "|"\r"|"\t"|"\n")*
"E"
>
}
Expression expression():
{
String exp;
Expression ret = null;
}
{
<EXP>
{ exp = token.image; }
{ int b = exp.indexOf("(") + 1; }
{ int e = exp.lastIndexOf(")"); }
{ ret = new Expression( exp.substring(b,e) ); }
{ return ret; }
}
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