def match(self, lexer: Lexer, debug: int = 0, partial=True):
if debug:
print(' ' * (debug - 1) +
f'### Group {self.name}.match(), calling super\'s match()')
tree = Ast(self.name, lexer.current_position(), grammars=[])
if lexer.current_token is None\
or lexer.current_token.spelling == '_EOF':
if self.repeat[0] == 0:
return tree
return None
lexer.anchor()
repetition = 0
if self.repeat[1] == -1:
# can repeat for infinite times: grammar* | grammar+ | grammar{a,}
while True:
nodes = super().match(lexer, debug)
if nodes is None:
break
tree.extend(nodes)
repetition += 1
if lexer.current_token is None:
break
else:
# repeat for limited times: grammar{a, b} | grammar{a} | [grammar]
while True:
if repetition >= self.repeat[1]:
break
nodes = super().match(lexer, debug)
if nodes is None:
break
tree.extend(nodes)
repetition += 1
if lexer.current_token is None:
break
if repetition < self.repeat[0]:
# if actual repetition is smaller than minimum times
if debug:
print(
' ' * (debug - 1) +
f'--- Group {self.name}.match() FAILED in minimal repetition)'
)
lexer.backward()
if debug:
print(
f'<<< lexer backwarded, current token: {lexer.current_token}'
)
return None
if debug:
print(' ' * (debug - 1) + f'+++ Group {self.name}.match() SUCCESS')
lexer.release_anchor()
return tree
def match(self, lexer: Lexer, debug: int = 0, partial=True):
"""
try to match lexer's current token with a production list in
productions
return AST instance: match SUCCESS with a production list in
productions
return None: match FAILED with whole productions
"""
tree = Ast(self.name, lexer.current_position(), grammars=[])
recursive_productions = []
for production_list in self.productions:
lexer.anchor()
if debug:
print(' ' * (
debug - 1) + f'### {self.name}.match() with production_list: {production_list}')
# productions: [[G1, G2], [G3, G4], ...] <-> G1 G2 | G3 G4 | ...
#
# try to match all tokes with a production_list, mark the tracker
# case 1: matched & break loop
# case 2: unmatched, try next production_list in productions until
# loop ends and function returns `None`
success = self.build_ast(tree, lexer, production_list,
recursive_productions,
debug) if debug else self.build_ast(tree,
lexer,
production_list,
recursive_productions)
if success is True or success is None:
# success case or Epsilon case
if debug:
print(
' ' * (debug - 1) + f'+++ {self.name}.match() SUCCESS')
break
else:
# failed case
continue
else:
if debug:
print(' ' * (debug - 1) + f'--- {self.name}.match() FAILED')
return None
# one production_list is fully matched, pop anchor stack by one
lexer.release_anchor()
if lexer.current_token is None or tree.children or partial:
return tree
return None