correct epsilon checks

Author: bygu4

pyformlang/cfg/cfg.py

@@ -659,8 +659,6 @@ def contains(self, word: Iterable[Hashable]) -> bool:
         """
         # Remove epsilons
         word = [to_terminal(x) for x in word if x != Epsilon()]
-        if not word:
-            return self.generate_epsilon()
         cyk_table = CYKTable(self, word)
         return cyk_table.generate_word()
 

pyformlang/finite_automaton/tests/test_epsilon.py

@@ -16,3 +16,4 @@ def test_epsilon(self):
         symb = Symbol(0)
         assert eps0 == eps1
         assert eps0 != symb
+        assert "epsilon" == Epsilon()

pyformlang/objects/cfg_objects/epsilon.py

@@ -3,6 +3,7 @@
 from typing import Any
 
 from .terminal import Terminal
+from ..finite_automaton_objects.epsilon import EPSILON_SYMBOLS
 
 
 class Epsilon(Terminal):
@@ -12,7 +13,7 @@ def __init__(self) -> None:
         super().__init__("epsilon")
 
     def __eq__(self, other: Any) -> bool:
-        return isinstance(other, Epsilon)
+        return isinstance(other, Epsilon) or other in EPSILON_SYMBOLS
 
     def __hash__(self) -> int:
         return super().__hash__()

pyformlang/objects/cfg_objects/utils.py

@@ -4,7 +4,7 @@
 
 from .variable import Variable
 from .terminal import Terminal
-from .epsilon import Epsilon
+from .epsilon import Epsilon, EPSILON_SYMBOLS
 
 
 def to_variable(given: Hashable) -> Variable:
@@ -18,6 +18,6 @@ def to_terminal(given: Hashable) -> Terminal:
     """ Transformation into a terminal """
     if isinstance(given, Terminal):
         return given
-    if given == "epsilon":
+    if given in EPSILON_SYMBOLS:
         return Epsilon()
     return Terminal(given)

pyformlang/objects/finite_automaton_objects/epsilon.py

@@ -6,6 +6,8 @@
 
 from .symbol import Symbol
 
+EPSILON_SYMBOLS = ["epsilon", "ɛ"]
+
 
 class Epsilon(Symbol):
     """ An epsilon transition
@@ -21,7 +23,7 @@ def __init__(self) -> None:
         super().__init__("epsilon")
 
     def __eq__(self, other: Any) -> bool:
-        return isinstance(other, Epsilon)
+        return isinstance(other, Epsilon) or other in EPSILON_SYMBOLS
 
     def __hash__(self) -> int:
-        return hash("EPSILON TRANSITION")
+        return super().__hash__()

pyformlang/objects/finite_automaton_objects/utils.py

@@ -4,7 +4,7 @@
 
 from .state import State
 from .symbol import Symbol
-from .epsilon import Epsilon
+from .epsilon import Epsilon, EPSILON_SYMBOLS
 
 
 def to_state(given: Hashable) -> State:
@@ -30,6 +30,6 @@ def to_symbol(given: Hashable) -> Symbol:
     """
     if isinstance(given, Symbol):
         return given
-    if given in ("epsilon", "ɛ"):
+    if given in EPSILON_SYMBOLS:
         return Epsilon()
     return Symbol(given)

pyformlang/objects/pda_objects/epsilon.py

@@ -3,6 +3,7 @@
 from typing import Any
 
 from .stack_symbol import StackSymbol
+from ..finite_automaton_objects.epsilon import EPSILON_SYMBOLS
 
 
 class Epsilon(StackSymbol):
@@ -12,7 +13,7 @@ def __init__(self) -> None:
         super().__init__("epsilon")
 
     def __eq__(self, other: Any) -> bool:
-        return isinstance(other, Epsilon)
+        return isinstance(other, Epsilon) or other in EPSILON_SYMBOLS
 
     def __hash__(self) -> int:
         return super().__hash__()

pyformlang/objects/pda_objects/utils.py

@@ -5,7 +5,7 @@
 from .state import State
 from .symbol import Symbol
 from .stack_symbol import StackSymbol
-from .epsilon import Epsilon
+from .epsilon import Epsilon, EPSILON_SYMBOLS
 
 
 def to_state(given: Hashable) -> State:
@@ -19,7 +19,7 @@ def to_symbol(given: Hashable) -> Symbol:
     """ Convert to a symbol """
     if isinstance(given, Symbol):
         return given
-    if given == "epsilon":
+    if given in EPSILON_SYMBOLS:
         return Epsilon()
     return Symbol(given)
 
@@ -28,6 +28,6 @@ def to_stack_symbol(given: Hashable) -> StackSymbol:
     """ Convert to a stack symbol """
     if isinstance(given, StackSymbol):
         return given
-    if given == "epsilon":
+    if given in EPSILON_SYMBOLS:
         return Epsilon()
     return StackSymbol(given)