grammar.xpg

grammar : ((name(NAME) assignment(ASSIGNMENT) expression) / ~comment(COMMENT))+
expression : first(sub_expr) rest(sequence / choice)?
choice = (combinator(SLASH) sub_expr)+
sequence = (combinator(NOT_SLASH) sub_expr !ASSIGNMENT)+
sub_expr = noncapture(TILDE)? assertion(ASSERTION)? (group / symbol(SYMBOL)) quantifier(QUANTIFIER)
group : name(NAME &L_PAREN)? L_PAREN expression R_PAREN

# mixed patterns
ASSERTION = AMPERSAND / EXCLAMATION
QUANTIFIER = (QUESTION / ASTERISK / PLUS)?
COMMENT = HASHTAG EXCEPT_LINE_BREAK
SYMBOL = REGEXP / DYNAMIC_RULE / LITERAL / NAME
ASSIGNMENT = COLON / EQUAL 
REGEXP = LOWER_R LITERAL

# patterns
NAME = r'[a-zA-Z0-9_]+'
LITERAL = r'''([^'']|(''''))*'''
NOT_SLASH = r'[^/]'
EXCEPT_LINE_BREAK = r'[^\n]*'
DYNAMIC_RULE = r'SCRIPT(\.[a-zA-Z0-9_]+)+'

# symbols
LOWER_R = 'r'
L_PAREN = '('
R_PAREN = ')'
COLON = SCRIPT.COLON
EQUAL = '='
TILDE = '~'
SLASH = '/'
QUESTION = '?'
ASTERISK = '*'
PLUS = '+'
AMPERSAND = SCRIPT.AMPERSAND
EXCLAMATION = SCRIPT.EXCLAMATION
HASHTAG = '#'

SKIP = r'\s*'
SCRIPT = './parser_ext'