1. General use

This is just an overview, consult the JavaDoc for more details.

1Grammar grammar = new Grammar();                      ①
 
NonterminalSymbol S = grammar.getNonterminal("S");    ②
NonterminalSymbol A = grammar.getNonterminal("A");
5NonterminalSymbol B = grammar.getNonterminal("B");
NonterminalSymbol X = grammar.getNonterminal("X");
NonterminalSymbol Y = grammar.getNonterminal("Y");
 
Rule s1 = new Rule(S, A);         ③
10grammar.addRule(s1);              ④
 
grammar.addRule(S, B);                                ⑤
grammar.addRule(A, TerminalSymbol.ch('a'), X);        ⑥
grammar.addRule(A, TerminalSymbol.ch('b'), X);
15grammar.addRule(B, TerminalSymbol.ch('b'), X);
grammar.addRule(X, TerminalSymbol.ch('x'));
grammar.addRule(Y, TerminalSymbol.ch('y'));
 
grammar.close();                                      ⑦
20 
HygieneReport report = grammar.checkHygiene(S);       ⑧
if (!report.isClean()) {
    // TODO: deal with undefined,
    // unused, and unproductive items
25}
 
EarleyParser parser = grammar.getParser(S);           ⑨
 
EarleyResult result = parser.parse("bx");             ⑩
30 
if (result.succeeded()) {                             ⑪
    ParseForest forest = result.getForest();          ⑫
    ParseTree tree = forest.parse();                  ⑬
 
35    // TODO: do something with the tree.
 
    if (forest.isAmbiguous()) {                       ⑭
        long totalParses = forest.getTotalParses();
        // TODO: deal with multiple parses
40    }
} else {
    // TODO: deal with failure
}

①: Create a Grammar.
②: Use the grammar to create nonterminal symbols.
③: Create rules mapping each nonterminal symbol to zero or more other symbols.
④: Add the rules to the grammar.
⑤: You can also just use the addRule method to add the symbols and their mappings directly.
⑥: Several flavors of TerminalSymbol are supported out-of-the-box and the set of Tokens is extensible.
⑦: Close the grammar when you’re finished adding to it. After a grammar is closed, it cannot be modified.
⑧: Hygiene problems with a closed grammar will generate warning messages through the logging framework. Hygiene problems include undefined or unused symbols as well as unproductive symbols and rules.
⑨: Create a parser.
⑩: Parse some input.
⑪: Examine the results.
⑫: Obtain the forest.
⑬: Get the (first) parse tree.
⑭: If the parse was ambiguous, you can get additional parse trees.