correct fcfg production properties and adding

Author: bygu4

pyformlang/fcfg/fcfg.py

@@ -59,29 +59,26 @@ class FCFG(CFG):
     """
 
     def __init__(self,
-                 variables: AbstractSet[Variable] = None,
-                 terminals: AbstractSet[Terminal] = None,
-                 start_symbol: Variable = None,
-                 productions: Iterable[FeatureProduction] = None) -> None:
+                 variables: AbstractSet[Hashable] = None,
+                 terminals: AbstractSet[Hashable] = None,
+                 start_symbol: Hashable = None,
+                 productions: Iterable[Production] = None) -> None:
         super().__init__(variables, terminals, start_symbol, productions)
         self._productions: Set[FeatureProduction]
 
-    def __predictor(self,
-                    state: State,
-                    chart: List[List[State]],
-                    processed: StateProcessed) -> None:
-        # We have an incomplete state and the next token is a variable
-        # We must ask to process the variable with another rule
-        end_idx = state.positions[1]
-        next_var = state.production.body[state.positions[2]]
-        for production in self._productions:
-            if production.head == next_var:
-                new_state = State(production,
-                                  (end_idx, end_idx, 0),
-                                  production.features,
-                                  ParseTree(production.head))
-                if processed.add(end_idx, new_state):
-                    chart[end_idx].append(new_state)
+    @property
+    def feature_productions(self) -> Set[FeatureProduction]:
+        """ Gets the feature productions of the grammar """
+        return self._productions
+
+    def add_production(self, production: Production) -> None:
+        """ Adds given production to the grammar """
+        if not isinstance(production, FeatureProduction):
+            production = FeatureProduction(production.head,
+                                           production.body,
+                                           FeatureStructure(),
+                                           [FeatureStructure()])
+        super().add_production(production)
 
     def contains(self, word: Iterable[Hashable]) -> bool:
         """ Gives the membership of a word to the grammar
@@ -212,6 +209,23 @@ def _read_line(cls,
             production = FeatureProduction(head, body, head_fs, all_body_fs)
             productions.add(production)
 
+    def __predictor(self,
+                    state: State,
+                    chart: List[List[State]],
+                    processed: StateProcessed) -> None:
+        # We have an incomplete state and the next token is a variable
+        # We must ask to process the variable with another rule
+        end_idx = state.positions[1]
+        next_var = state.production.body[state.positions[2]]
+        for production in self._productions:
+            if production.head == next_var:
+                new_state = State(production,
+                                  (end_idx, end_idx, 0),
+                                  production.features,
+                                  ParseTree(production.head))
+                if processed.add(end_idx, new_state):
+                    chart[end_idx].append(new_state)
+
 
 def _split_text_conditions(head_text: str) -> Tuple[str, str]:
     if head_text[-1] != "]":

pyformlang/fcfg/tests/test_fcfg.py

@@ -1,6 +1,7 @@
 """Test a FCFG"""
 
-from pyformlang.cfg import Variable, Terminal
+from pyformlang.cfg import Variable, Terminal, Production
+from pyformlang.cfg import DerivationDoesNotExist
 from pyformlang.cfg.parse_tree import ParseTree
 from pyformlang.cfg.llone_parser import NotParsableException
 from pyformlang.fcfg.fcfg import FCFG
@@ -32,6 +33,30 @@ def fcfg_text() -> str:
 class TestFCFG:
     """Test a FCFG"""
 
+    def test_creation(self):
+        """ Tests creation of FCFG """
+        variable0 = Variable(0)
+        terminal0 = Terminal("a")
+        prod0 = Production(variable0, [terminal0, Terminal("A"), Variable(1)])
+        fcfg = FCFG({variable0}, {terminal0}, variable0, {prod0})
+        assert fcfg is not None
+        assert len(fcfg.variables) == 2
+        assert len(fcfg.terminals) == 2
+        assert len(fcfg.productions) == 1
+        assert len(fcfg.feature_productions) == 1
+        assert fcfg.productions == fcfg.feature_productions
+        assert fcfg.is_empty()
+        assert all(isinstance(prod, FeatureProduction)
+                   for prod in fcfg.productions)
+
+        fcfg = FCFG()
+        assert fcfg is not None
+        assert len(fcfg.variables) == 0
+        assert len(fcfg.terminals) == 0
+        assert len(fcfg.productions) == 0
+        assert len(fcfg.feature_productions) == 0
+        assert fcfg.is_empty()
+
     def test_contains(self):
         """Test containment"""
         # 1st: S -> NP VP
@@ -231,3 +256,28 @@ def test_copy(self, fcfg_text: str):
         assert fcfg.productions == fcfg_copy.productions
         assert fcfg.start_symbol == fcfg_copy.start_symbol
         assert fcfg is not fcfg_copy
+
+    def test_get_leftmost_derivation(self):
+        ter_a = Terminal("a")
+        ter_b = Terminal("b")
+        var_s = Variable("S")
+        var_a = Variable("A")
+        var_b = Variable("B")
+        var_c = Variable("C")
+        productions = [Production(var_s, [var_c, var_b]),
+                       Production(var_c, [var_a, var_a]),
+                       Production(var_a, [ter_a]),
+                       Production(var_b, [ter_b])
+                       ]
+        fcfg = FCFG(productions=productions, start_symbol=var_s)
+        parse_tree = fcfg.get_cnf_parse_tree([ter_a, ter_a, ter_b])
+        derivation = parse_tree.get_leftmost_derivation()
+        assert derivation == \
+                         [[var_s],
+                          [var_c, var_b],
+                          [var_a, var_a, var_b],
+                          [ter_a, var_a, var_b],
+                          [ter_a, ter_a, var_b],
+                          [ter_a, ter_a, ter_b]]
+        with pytest.raises(DerivationDoesNotExist):
+            fcfg.get_cnf_parse_tree([])