Building the Parser
In order for the build.xml to work, the project first has to be run through eclipse with
the ANTLR plugin.
You can download the antlr plugin from: http://antlreclipse.sourceforge.net/.
Follow the steps for installing it (note that the screenshots are for an older Eclipse) and
use the context menu for the project to Toggle ANTLR Project Nature. When it's turned
on you'll see antlers (brown wavy line) above the project's icon in the Package Explorer
and/or Navigator views. If it's turned on, changes to the expression.g grammar file will
automatically cause the Java files to be regenerated.
Eventually I need to automate the build.xml to perform this task.