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 build_ast(self, tree: Ast, lexer: Lexer, production_list: list,
recursive_productions: list = None, debug: int = 0):
"""
build ast tree on the given instance (parameter `tree`)
return True: SUCCESS, tree is appended with nodes
return False: FAILED, and tree is untouched
return None: Epsilon
"""
if debug:
print(' ' * (debug - 1) + f'### {self.name}.build_ast()')
for grammar in production_list:
nodes = grammar.match(lexer,
debug + 4) if debug else grammar.match(lexer)
# this grammar not matched:
# 1. abandon whole production_list and skipped loop
# 2. lexer setup rollback flag
if nodes is None:
if debug:
print(' ' * (
debug - 1) + f'--- {self.name}.build_ast() with grammar <{grammar}> FAILED')
tree.empty()
lexer.backward()
if debug:
print(
f'<<< lexer backwarded, current token: {lexer.current_token}')
return False
if nodes == '_E':
# Epsilon
if debug:
print(' ' * (debug - 1) + f'+++ Epsilon match')
tree.append(Ast('Epsilon', lexer.current_token.position,
grammar='_e'))
return None
if isinstance(grammar, Group):
# grammar is a Group
if not self.ignore_set:
tree.extend(nodes)
else:
for node in nodes:
if node.name not in self.ignore_set:
tree.append(node)
else:
# grammar is a Token, only one production hence nodes is
# actually a `node`
if not self.ignore_set or nodes.name not in self.ignore_set:
tree.append(nodes)
# all grammar in current production_list matched, operation SUCCESS
if debug:
print(' ' * (debug - 1) + f'+++ {self.name}.build_ast() SUCCESS')
return True