def test_given_states_followed_by_terminals_then_complete_closure(
self) -> None:
grammar = Grammar(Rule('A', ['X', 'a']), Rule('A', ['A', 'X']),
Rule('X', ['x']))
result = closure_for(grammar, RuleState(0, 1, {'$'}),
RuleState(1, 2, {'$'}))
self.assertEqual({RuleState(0, 1, {'$'}),
RuleState(1, 2, {'$'})}, result)
def test_given_states_followed_by_recursion_then_closure_includes_all_lookaheads(
self) -> None:
grammar = Grammar(Rule('A', ['a', 'A']), Rule('A', ['A', 'A']))
result = closure_for(grammar, RuleState(0, 1, {'$'}))
expected = {
RuleState(0, 1, {'$'}),
RuleState(1, 0, {'$', 'a'}),
RuleState(0, 0, {'$', 'a'})
}
self.assertEqual(expected, result)
def test_given_states_followed_by_references_then_closure_includes_references(
self) -> None:
grammar = Grammar(Rule('A', ['x', 'B']), Rule('B', ['C']),
Rule('C', ['x']))
result = closure_for(grammar, RuleState(0, 1, {'$'}))
expected = {
RuleState(0, 1, {'$'}),
RuleState(1, 0, {'$'}),
RuleState(2, 0, {'$'})
}
self.assertEqual(expected, result)
def test_given_lookaheads_then_closure_simplifies_lookaheads(self) -> None:
grammar = Grammar(Rule('A', ['a']), Rule('A', ['B', 'B']),
Rule('B', ['b']), Rule('B', ['A', 'B']))
result = closure_for(grammar, RuleState(1, 1, {'x', 'y'}))
expected = {
RuleState(1, 1, {'x', 'y'}),
RuleState(2, 0, {'x', 'y', 'b', 'a'}),
RuleState(3, 0, {'x', 'y', 'b', 'a'}),
RuleState(0, 0, {'b', 'a'}),
RuleState(1, 0, {'b', 'a'})
}
self.assertEqual(expected, result)
def test_given_states_in_cycles_then_closure_includes_all_lookaheads(
self) -> None:
grammar = Grammar(Rule('C', ['A']), Rule('A', ['B', 'B']),
Rule('B', ['C']), Rule('C', ['c']), Rule('A', ['a']),
Rule('B', ['b']))
result = closure_for(grammar, RuleState(1, 1, {'$'}))
expected = {
RuleState(1, 1, {'$'}),
RuleState(2, 0, {'$', 'c', 'a', 'b'}),
RuleState(5, 0, {'$', 'c', 'a', 'b'}),
RuleState(0, 0, {'$', 'c', 'a', 'b'}),
RuleState(3, 0, {'$', 'c', 'a', 'b'}),
RuleState(1, 0, {'$', 'c', 'a', 'b'}),
RuleState(4, 0, {'$', 'c', 'a', 'b'})
}
self.assertEqual(expected, result)
def graph_for(grammar: Grammar) -> ClosureGraph:
from cmaj.parser.closure import closure_for, successors_for
graph = ClosureGraph()
fringe = {closure_for(grammar, RuleState.start(grammar))}
while fringe:
source = fringe.pop()
graph.add_closure(source)
successors = successors_for(grammar, source)
fringe |= {
target
for target in successors.values() if target not in graph
}
for symbol, target in successors.items():
graph.add_edge(source, symbol, target)
return graph
def test_given_state_followed_by_two_references_then_lookahead_of_reference(
self) -> None:
grammar = Grammar(Rule('A', ['B', 'B']), Rule('B', ['b']))
result = closure_for(grammar, RuleState(0, 0, {'$'}))
self.assertEqual({RuleState(0, 0, {'$'}),
RuleState(1, 0, {'b'})}, result)
def test_given_grammar_with_single_rule_then_complete_closure(
self) -> None:
grammar = Grammar(Rule('X', ['x']))
result = closure_for(grammar, RuleState(0, 0, {'$'}))
self.assertEqual({RuleState(0, 0, {'$'})}, result)
