[antlr-interest] Tree grammars & optional AST nodes

[Nicolas Rouquette]

An ANTLR3 / ANTLRWorks newbie question, if I may.

The Java1.5 ANTLR3 grammar has rules like this:

expression
:	conditionalExpression (assignmentOperator expression)?
	;
conditionalExpression
    :   conditionalOrExpression ( '?' expression ':' expression )?
	;