Verified Commit 4ba5984f authored by Vladimír Štill's avatar Vladimír Štill
Browse files

CFL: Fix removal of simple rules & more tests

parent dffa3596

grammars_cfg.py

+18 −8
Original line number Diff line number Diff line
@@ -33,6 +33,15 @@ class GeneratesResult: 
    def __bool__(self) -> bool:

        return self.value



    # for the sake of assertions/pytest

    def __repr__(self) -> str:

        info = ""

        if self.cyk_table is not None:

            inc = "∈" if self.value else "∉"

            info = f" ({self.cnf_cfg.init.name} {inc} " \

                   f"{set(x.name for x in self.cyk_table[-1][0])})"

        return f"{self.value}{info}"





class InfinityType:

    pass
@@ -292,14 +301,15 @@ class CFG: 
        simple_to: Dict[Nonterminal, Set[Nonterminal]] =\

            {n: {n} for n in self.nonterminals}



        added = True

        while added:

            added = False

            for src, prod in self.productions():

                if len(prod) == 1 and prod[0] in self.nonterminals \

                        and prod[0] not in simple_to[src]:

                    added = True

                    simple_to[src].add(typing.cast(Nonterminal, prod[0]))

        for tracker in ChangeTracker():

            for src_orig in self.nonterminals:

                # make a copy to avoid error for changing during iteraton

                for src in list(simple_to[src_orig]):

                    for prod in self.rules.get(src, []):

                        if len(prod) == 1 and isinstance(prod[0], Nonterminal)\

                                and prod[0] not in simple_to[src_orig]:

                            tracker.changed()

                            simple_to[src_orig].add(prod[0])



        new_rules: CFG.Rules = dict()

        for src in self.nonterminals:

test_cfl_cfg.py

+34 −0
Original line number Diff line number Diff line
@@ -52,6 +52,23 @@ def test_generates(): 
    go(g2)





def test_remove_simple() -> None:

    g = cfl.CFG({S, A, B, C}, {a},

                {S: {(A,)},

                 A: {(B, C), (B,), (C,)},

                 B: {(a, B), (a,)},

                 C: {(a, a, C), (a, a)}},

                S)

    print(g)

    gs = g.remove_simple_rules()

    print(gs)

    assert (B, C) in gs.rules[gs.init]

    assert (a, B) in gs.rules[gs.init]

    assert (a,) in gs.rules[gs.init]

    assert (a, a, C) in gs.rules[gs.init]

    assert (a, a) in gs.rules[gs.init]





def test_remove_eps():

    g = g2.epsilon_normal_form()

    assert g.init == g1.init
@@ -59,6 +76,23 @@ def test_remove_eps(): 
    assert g.nonterminals == g1.nonterminals

    assert g.rules == g1.rules



    g = cfl.CFG({S, A, B}, {a, b},

                {S: {(A, B)},

                 A: {(a, A), ()},

                 B: {(b, B), ()}},

                S)

    ge = g.epsilon_normal_form()

    print(ge.proper())

    assert ge.init != S

    assert () in ge.rules[ge.init]

    assert ge.generates("")

    print(ge.generates("aa").cnf_cfg)

    assert ge.generates("aa")

    assert ge.generates("bb")

    assert ge.generates("ab")

    assert not ge.generates("aba")

    assert not ge.generates("ba")





def test_equal():

    R = Nonterminal("R")