Module io.jenetics.ext
Package io.jenetics.ext.grammar

Class Bnf

java.lang.Object
io.jenetics.ext.grammar.Bnf
public final class Bnf extends Object
This class contains methods for parsing and formatting context-free grammars in BNF format. 
final Cfg<String> grammar = Bnf.parse("""
    <expr> ::= <num> | <var> | '(' <expr> <op> <expr> ')'
    <op>   ::= + | - | * | /
    <var>  ::= x | y
    <num>  ::= 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9
    """
);
Since:
7.1
Version:
7.1

  • Method Details

    • parse

      public static Cfg<String> parse(String grammar)
      Parses the given BNF grammar string to a Cfg object. The following example shows the grammar of a simple arithmetic expression. 
      
 <expr> ::= <num> | <var> | '(' <expr> <op> <expr> ')'
 <op>   ::= + | - | * | /
 <var>  ::= x | y
 <num>  ::= 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9
      Parameters:
      grammar - the BNF grammar string
      Returns:
      the parsed BNF object
      Throws:
      ParsingException - if the given grammar is invalid
      NullPointerException - it the given grammar string is null

    • format

      public static String format(Cfg<?> grammar)
      Formats the given CFG as BNF grammar string.
      Parameters:
      grammar - the CFG to format as BNF
      Returns:
      the BNF formatted grammar string
      Throws:
      NullPointerException - if the give grammar is null