def test_zero_or_more(self): len_eq(ZeroOrMore(Literal('b')).match(''), 0) # zero len_eq(ZeroOrMore(Literal('b')).match('bbb'), 3) # more len_eq(Regex('^').match(''), 0) # Validate the next test. # Try to make it loop infinitely using a zero-length contained expression: len_eq(ZeroOrMore(Regex('^')).match(''), 0)
def _expressions_from_rules(self, rule_syntax, custom_rules): """Return the rules for parsing the grammar definition syntax. Return a 2-tuple: a dict of rule names pointing to their expressions, and then the top-level expression for the first rule. """ # Hard-code enough of the rules to parse the grammar that describes the # grammar description language, to bootstrap: comment = Regex(r'#[^\r\n]*', name='comment') meaninglessness = OneOf(Regex(r'\s+'), comment, name='meaninglessness') _ = ZeroOrMore(meaninglessness, name='_') equals = Sequence(Literal('='), _, name='equals') label = Sequence(Regex(r'[a-zA-Z_][a-zA-Z_0-9]*'), _, name='label') reference = Sequence(label, Not(equals), name='reference') quantifier = Sequence(Regex(r'[*+?]'), _, name='quantifier') # This pattern supports empty literals. TODO: A problem? spaceless_literal = Regex(r'u?r?"[^"\\]*(?:\\.[^"\\]*)*"', ignore_case=True, dot_all=True, name='spaceless_literal') literal = Sequence(spaceless_literal, _, name='literal') regex = Sequence(Literal('~'), literal, Regex('[ilmsuxa]*', ignore_case=True), _, name='regex') atom = OneOf(reference, literal, regex, name='atom') quantified = Sequence(atom, quantifier, name='quantified') term = OneOf(quantified, atom, name='term') not_term = Sequence(Literal('!'), term, _, name='not_term') term.members = (not_term, ) + term.members sequence = Sequence(term, OneOrMore(term), name='sequence') or_term = Sequence(Literal('/'), _, term, name='or_term') ored = Sequence(term, OneOrMore(or_term), name='ored') expression = OneOf(ored, sequence, term, name='expression') rule = Sequence(label, equals, expression, name='rule') rules = Sequence(_, OneOrMore(rule), name='rules') # Use those hard-coded rules to parse the (more extensive) rule syntax. # (For example, unless I start using parentheses in the rule language # definition itself, I should never have to hard-code expressions for # those above.) rule_tree = rules.parse(rule_syntax) # Turn the parse tree into a map of expressions: return RuleVisitor().visit(rule_tree)
def test_zero_or_more_zero(self): """Test the 0 case of ``ZeroOrMore``; it should still return a node.""" expr = ZeroOrMore(Literal('a'), name='zero') text = '' eq_(expr.match(text), Node('zero', text, 0, 0))
def test_zero_or_more_zero(self): """Test the 0 case of ``ZeroOrMore``; it should still return a node.""" expr = ZeroOrMore(Literal("a"), name="zero") text = "" eq_(expr.match(text), Node("zero", text, 0, 0))