Added trivial grammar E_NP_ for testing.

spottedMetal · spottedMetal · commit 20ecaa25d751 · 2007-07-17T17:46:38.000Z
Fixed error in Chart parses method, where it would
incorrectly return some parses that did not start at the beginning
of the input (and therefore did not span the whole input).
diff --git a/nlp.py b/nlp.py
@@ -78,6 +78,11 @@ def __repr__(self):
     V = 'saw | liked | feel'
     ))
 
+E_NP_ = Grammar('E_NP_', # another trivial grammar for testing
+              Rules(NP = 'Adj NP | N'),
+              Lexicon(Adj = 'happy | handsome | hairy',
+                      N = 'man'))
+
 def generate_random(grammar=E_, s='S'):
     """Replace each token in s by a random entry in grammar (recursively).
     This is useful for testing a grammar, e.g. generate_random(E_)"""
@@ -113,14 +118,20 @@ def __init__(self, grammar, trace=False):
         update(self, grammar=grammar, trace=trace)
 
     def parses(self, words, S='S'):
-        """Return a list of parses; words can be a list or string."""
+        """Return a list of parses; words can be a list or string.
+        >>> chart = Chart(E_NP_)
+        >>> chart.parses('happy man', 'NP')
+        [[0, 2, 'NP', [('Adj', 'happy'), [1, 2, 'NP', [('N', 'man')], []]], []]]
+        """
         if isinstance(words, str):
             words = words.split()
         self.parse(words, S)
         # Return all the parses that span the whole input
+        # 'span the whole input' => begin at 0, end at len(words)
         return [[i, j, S, found, []]
                 for (i, j, lhs, found, expects) in self.chart[len(words)]
-                if lhs == S and expects == []]
+                # assert j == len(words)
+                if i == 0 and lhs == S and expects == []]
 
     def parse(self, words, S='S'):
         """Parse a list of words; according to the grammar.
