def _rule_state_to_string(rule_state: RuleState,
grammar: Grammar) -> Tuple[str, str, str]:
rule = grammar.rule_at(rule_state.rule_index)
key = rule.key
processed_str = ' '.join(rule.symbols[:rule_state.num_processed])
unprocessed_str = ' '.join(rule.symbols[rule_state.num_processed:])
lookaheads_str = ' '.join(
[str(symbol) for symbol in rule_state.lookaheads])
return f'{key}', f'{processed_str}⬤{unprocessed_str}', f'{lookaheads_str}'
def parse(tokens: List[Node], grammar: Grammar, table: ParseTable) -> Node:
from cmaj.parser.table import Action
assert table.num_rows > 0
stack: Stack = []
row = 0
tokens = tokens + [Node(Grammar.AUGMENTED_EOF)]
token_index = 0
while True:
token = tokens[token_index]
action = table.action(row, token.key)
if action is None:
raise ParserError(f'Unexpected token: {tokens[token_index]!r}')
elif action.key == Action.ACCEPT:
break
elif action.key == Action.SHIFT:
stack.append((row, tokens[token_index]))
row = action.index
token_index += 1
elif action.key == Action.GOTO:
row = action.index
elif action.key == Action.REDUCE:
rule_index = action.index
rule = grammar.rule_at(rule_index)
stack, row, nodes = _reduce_stack(stack, rule)
node = _reduce_nodes(nodes, rule)
stack.append((row, node))
action = table.action(row, node.key)
assert action.key == Action.GOTO
row = action.index
else:
raise ParserError(f'Unexpected parser action {action!r} for token: {tokens[token_index]!r}')
if len(stack) != 1:
raise ParserError(f'Found unprocessed tokens: {_to_symbols(stack)!r}')
return stack[0][1]
def __init__(self, state: RuleState, grammar: Grammar) -> None:
rule = grammar.rule_at(state.rule_index)
self._key = rule.key
self._unprocessed_symbols = rule.symbols[state.num_processed:]
