package oops3;

public class XbnfParser {
%%

# XBNF-style grammar for extended EBNF

# ( x )			for precedence
# x | y			for mutually exclusive alternatives
# [ x, y ]		for inclusive alternatives (unordered subset)
# [ x, y ] / delim	... with delimiters
# { x, y }		for all alternatives (unordered full set)
# { x, y } / delim	... with delimiters
# x ?			for optional items
# x +			for one or more iterations
# x *			for zero or more iterations
# x number		for a number of iterations
# x from..to		for a range of iterations
# x ..max		for zero to max iterations
# x min..		for min or more iterations
# x ..			for zero or more iterations
# x range / delim	... any (non-singleton) range with delimiters

# skip patterns

<void>      Comment = '#.*';
<void>      WhiteSpace = '[ \r\t\n]+';

# token patterns (these are placeholders for a hand-crafted scanner)

<String>    Prolog = '.*%%';
<String>    Id = '[a-zA-Z_][-a-zA-Z_0-9.$]*';
<String>    String = '\'([^\'\\\r\n]|\\.)*\'';
<Integer>   Number = '[1-9][0-9]*';
<String>    Epilog = '%%.*';

# RFC-style rules

<Parser>    parser: Prolog rule+ Epilog;
<Node>      rule: type? Id ( pattern | rhs ) ';';
<Type>      type: '<' ( Id ( ':' Id +/ ',' )? '>' '?'? | '>' );
            pattern: '=' String;
            rhs: ':' xor;
<Node>      xor: sequence +/ '|';
<Sequence>  sequence: term+;
<Literal>   literal: String;
<Object>    optional: '?';
<Object>    some: '+' list?;
<Object>    many: '*' list?;
            list: '/' item;

# changed rules

<Node>      term: item range?;
<Node>      item: Id | literal | '(' xor ')' | or | and;
<Node>      or: '[' xor 2../ ',' ']' list?;
<Node>      and: '{' xor 2../ ',' '}' list?;
            range: range1 | range2 | optional | some | many;
<Object>    range1: Number ( '..' Number? list? | list )?;
<Object>    range2: '..' ( Number? list? )?;

%%
}