Move is_recursive() test to top-level grammar module

Author: ekaf

nltk/grammar.py

@@ -6,6 +6,7 @@
 #         Jason Narad <[email protected]>
 #         Peter Ljunglöf <[email protected]>
 #         Tom Aarsen <>
+#         Eric Kafe <[email protected]>
 # URL: <https://www.nltk.org/>
 # For license information, see LICENSE.TXT
 #
@@ -304,6 +305,9 @@ def rhs(self):
         """
         return self._rhs
 
+    def is_recursive(self):
+        return self.lhs() in self.rhs()
+
     def __len__(self):
         """
         Return the length of the right-hand side.
@@ -605,6 +609,12 @@ def productions(self, lhs=None, rhs=None, empty=False):
                 if prod in self._rhs_index.get(rhs, [])
             ]
 
+    def is_recursive(self):
+        for prod in self.productions():
+            if prod.is_recursive():
+                return True
+        return False
+
     def leftcorners(self, cat):
         """
         Return the set of all nonterminals that the given nonterminal

nltk/parse/generate.py

@@ -14,13 +14,6 @@
 from nltk.grammar import Nonterminal
 
 
-def is_recursive(grammar):
-    for prod in grammar.productions():
-        if prod.lhs() in prod.rhs():
-            return True
-    return False
-
-
 def generate(grammar, start=None, depth=None, n=None):
     """
     Generates an iterator of all sentences from a CFG.
@@ -34,7 +27,7 @@ def generate(grammar, start=None, depth=None, n=None):
     if not start:
         start = grammar.start()
     if depth is None:
-        if is_recursive(grammar):
+        if grammar.is_recursive():
             # This seems to be an almost maximal safe default with Python 3:
             depth = (sys.getrecursionlimit() // 3) - 3
         else: