Parsers consist of a set of parser rules in either a parser or a combined grammar. A Java application launches a parser by invoking the rule function, generated by ANTLR, associated with the desired start rule. The most basic rule is just a rule name followed by a single alternative terminated with a semicolon.
|||/** Javadoc comment can precede rule */|
|||retstat : 'return' expr ';' ;|
Rules can also have alternatives separated by the | operator.
|||| 'break' ';'|
|||| 'continue' ';'|
Alternatives are either a list of rule elements or empty. For example, here’s a rule with an empty alternative that makes the entire rule optional:
|||: 'extends' ID|
|||| // empty means other ...|